postgrespro
diff --git a/‎doc/src/sgml/config.sgml
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diff --git a/‎doc/src/sgml/mvcc.sgml
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Lines changed: 3 additions & 1 deletion
diff --git a/‎src/backend/storage/lmgr/predicate.c
Lines changed: 31 additions & 17 deletions b/‎src/backend/storage/lmgr/predicate.c
Lines changed: 31 additions & 17 deletions
diff --git a/‎src/backend/utils/misc/guc.c
Lines changed: 22 additions & 0 deletions b/‎src/backend/utils/misc/guc.c
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diff --git a/‎src/backend/utils/misc/postgresql.conf.sample
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diff --git a/‎src/include/storage/predicate.h
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@@ -7337,7 +7337,43 @@ dynamic_library_path = 'C:\tools\postgresql;H:\my_project\lib;$libdir'
         tables in a single serializable transaction. This parameter can
         only be set at server start.
        </para>
+      </listitem>
+     </varlistentry>
+
+     <varlistentry id="guc-max-pred-locks-per-relation" xreflabel="max_pred_locks_per_relation">
+      <term><varname>max_pred_locks_per_relation</varname> (<type>integer</type>)
+      <indexterm>
+       <primary><varname>max_pred_locks_per_relation</> configuration parameter</primary>
+      </indexterm>
+      </term>
+      <listitem>
+       <para>
+        This controls how many pages or tuples of a single relation can be
+        predicate-locked before the lock is promoted to covering the whole
+        relation.  Values greater than or equal to zero mean an absolute
+        limit, while negative values
+        mean <xref linkend="guc-max-pred-locks-per-transaction"> divided by
+        the absolute value of this setting.  The default is -2, which keeps
+        the behaviour from previous versions of <productname>PostgreSQL</>.
+        This parameter can only be set in the <filename>postgresql.conf</>
+        file or on the server command line.
+       </para>
+      </listitem>
+     </varlistentry>
 
+     <varlistentry id="guc-max-pred-locks-per-page" xreflabel="max_pred_locks_per_page">
+      <term><varname>max_pred_locks_per_page</varname> (<type>integer</type>)
+      <indexterm>
+       <primary><varname>max_pred_locks_per_page</> configuration parameter</primary>
+      </indexterm>
+      </term>
+      <listitem>
+       <para>
+        This controls how many rows on a single page can be predicate-locked
+        before the lock is promoted to covering the whole page.  The default
+        is 2.  This parameter can only be set in
+        the <filename>postgresql.conf</> file or on the server command line.
+       </para>
       </listitem>
      </varlistentry>
 
 
@@ -765,7 +765,9 @@ ERROR:  could not serialize access due to read/write dependencies among transact
        locks into a single relation-level predicate lock because the predicate
        lock table is short of memory, an increase in the rate of serialization
        failures may occur.  You can avoid this by increasing
-       <xref linkend="guc-max-pred-locks-per-transaction">.
+       <xref linkend="guc-max-pred-locks-per-transaction">,
+       <xref linkend="guc-max-pred-locks-per-relation">, and/or
+       <xref linkend="guc-max-pred-locks-per-page">.
       </para>
      </listitem>
      <listitem>
 
@@ -352,8 +352,15 @@ static OldSerXidControl oldSerXidControl;
 static SERIALIZABLEXACT *OldCommittedSxact;
 
 
-/* This configuration variable is used to set the predicate lock table size */
+/*
+ * These configuration variables are used to set the predicate lock table size
+ * and to control promotion of predicate locks to coarser granularity in an
+ * attempt to degrade performance (mostly as false positive serialization
+ * failure) gracefully in the face of memory pressurel
+ */
 int			max_predicate_locks_per_xact;		/* set by guc.c */
+int			max_predicate_locks_per_relation;	/* set by guc.c */
+int			max_predicate_locks_per_page;		/* set by guc.c */
 
 /*
  * This provides a list of objects in order to track transactions
@@ -437,7 +444,7 @@ static void RestoreScratchTarget(bool lockheld);
 static void RemoveTargetIfNoLongerUsed(PREDICATELOCKTARGET *target,
 						   uint32 targettaghash);
 static void DeleteChildTargetLocks(const PREDICATELOCKTARGETTAG *newtargettag);
-static int	PredicateLockPromotionThreshold(const PREDICATELOCKTARGETTAG *tag);
+static int	MaxPredicateChildLocks(const PREDICATELOCKTARGETTAG *tag);
 static bool CheckAndPromotePredicateLockRequest(const PREDICATELOCKTARGETTAG *reqtag);
 static void DecrementParentLocks(const PREDICATELOCKTARGETTAG *targettag);
 static void CreatePredicateLock(const PREDICATELOCKTARGETTAG *targettag,
@@ -2118,28 +2125,35 @@ DeleteChildTargetLocks(const PREDICATELOCKTARGETTAG *newtargettag)
 }
 
 /*
- * Returns the promotion threshold for a given predicate lock
- * target. This is the number of descendant locks required to promote
- * to the specified tag. Note that the threshold includes non-direct
- * descendants, e.g. both tuples and pages for a relation lock.
+ * Returns the promotion limit for a given predicate lock target.  This is the
+ * max number of descendant locks allowed before promoting to the specified
+ * tag. Note that the limit includes non-direct descendants (e.g., both tuples
+ * and pages for a relation lock).
+ *
+ * Currently the default limit is 2 for a page lock, and half of the value of
+ * max_pred_locks_per_transaction - 1 for a relation lock, to match behavior
+ * of earlier releases when upgrading.
  *
- * TODO SSI: We should do something more intelligent about what the
- * thresholds are, either making it proportional to the number of
- * tuples in a page & page
F438
s in a relation, or at least making it a
- * GUC. Currently the threshold is 3 for a page lock, and
- * max_pred_locks_per_transaction/2 for a relation lock, chosen
- * entirely arbitrarily (and without benchmarking).
+ * TODO SSI: We should probably add additional GUCs to allow a maximum ratio
+ * of page and tuple locks based on the pages in a relation, and the maximum
+ * ratio of tuple locks to tuples in a page.  This would provide more
+ * generally "balanced" allocation of locks to where they are most useful,
+ * while still allowing the absolute numbers to prevent one relation from
+ * tying up all predicate lock resources.
  */
 static int
-PredicateLockPromotionThreshold(const PREDICATELOCKTARGETTAG *tag)
+MaxPredicateChildLocks(const PREDICATELOCKTARGETTAG *tag)
 {
 	switch (GET_PREDICATELOCKTARGETTAG_TYPE(*tag))
 	{
 		case PREDLOCKTAG_RELATION:
-			return max_predicate_locks_per_xact / 2;
+			return max_predicate_locks_per_relation < 0
+				? (max_predicate_locks_per_xact
+				   / (-max_predicate_locks_per_relation)) - 1
+				: max_predicate_locks_per_relation;
 
 		case PREDLOCKTAG_PAGE:
-			return 3;
+			return max_predicate_locks_per_page;
 
 		case PREDLOCKTAG_TUPLE:
 
@@ -2194,8 +2208,8 @@ CheckAndPromotePredicateLockRequest(const PREDICATELOCKTARGETTAG *reqtag)
 		else
 			parentlock->childLocks++;
 
-		if (parentlock->childLocks >=
-			PredicateLockPromotionThreshold(&targettag))
+		if (parentlock->childLocks >
+			MaxPredicateChildLocks(&targettag))
 		{
 			/*
 			 * We should promote to this parent lock. Continue to check its
 
@@ -2199,6 +2199,28 @@ static struct config_int ConfigureNamesInt[] =
 		NULL, NULL, NULL
 	},
 
+	{
+		{"max_pred_locks_per_relation", PGC_SIGHUP, LOCK_MANAGEMENT,
+			gettext_noop("Sets the maximum number of predicate-locked pages and tuples per relation."),
+			gettext_noop("If more than this total of pages and tuples in the same relation are locked "
+						 "by a connection, those locks are replaced by a relation level lock.")
+		},
+		&max_predicate_locks_per_relation,
+		-2, INT_MIN, INT_MAX,
+		NULL, NULL, NULL
+	},
+
+	{
+		{"max_pred_locks_per_page", PGC_SIGHUP, LOCK_MANAGEMENT,
+			gettext_noop("Sets the maximum number of predicate-locked tuples per page."),
+			gettext_noop("If more than this number of tuples on the same page are locked "
+						 "by a connection, those locks are replaced by a page level lock.")
+		},
+		&max_predicate_locks_per_page,
+		2, 0, INT_MAX,
+		NULL, NULL, NULL
+	},
+
 	{
 		{"authentication_timeout", PGC_SIGHUP, CONN_AUTH_SECURITY,
 			gettext_noop("Sets the maximum allowed time to complete client authentication."),
 
@@ -593,6 +593,10 @@
 					# (change requires restart)
 #max_pred_locks_per_transaction = 64	# min 10
 					# (change requires restart)
+#max_pred_locks_per_relation = -2	# negative values mean
+					# (max_pred_locks_per_transaction
+					#  / -max_pred_locks_per_relation) - 1
+#max_pred_locks_per_page = 2            # min 0
 
 
 #------------------------------------------------------------------------------
 
@@ -22,6 +22,8 @@
  * GUC variables
  */
 extern int	max_predicate_locks_per_xact;
+extern int	max_predicate_locks_per_relation;
+extern int	max_predicate_locks_per_page;
 
 
 /* Number of SLRU buffers to use for predicate locking */