Using snapshot lsn

pct960 · pct960 · commit 5afae09a83ed · 2023-06-05T16:18:54.000-04:00
diff --git a/src/backend/access/transam/xact.c b/src/backend/access/transam/xact.c
@@ -2098,7 +2098,8 @@ StartTransaction(void)
 	VirtualTransactionId vxid;
 
 	//maxLSN = XLogGetMaxLSN(NULL);
-	maxLSN = GetInsertRecPtr();
+	//maxLSN = GetXLogInsertRecPtr();
+	maxLSN = GetCurrentSnapshotLSN();
 	//elog(INFO, "maxlsn init");
 
 	/*
diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c
@@ -2095,7 +2095,6 @@ GetSnapshotDataInitOldSnapshot(Snapshot snapshot)
 		 * If not using "snapshot too old" feature, fill related fields with
 		 * dummy values that don't require any locking.
 		 */
-		snapshot->lsn = InvalidXLogRecPtr;
 		snapshot->whenTaken = 0;
 	}
 	else
@@ -2105,10 +2104,11 @@ GetSnapshotDataInitOldSnapshot(Snapshot snapshot)
 		 * snapshot becomes old enough to need to fall back on the special
 		 * "old snapshot" logic.
 		 */
-		snapshot->lsn = GetXLogInsertRecPtr();
 		snapshot->whenTaken = GetSnapshotCurrentTimestamp();
 		MaintainOldSnapshotTimeMapping(snapshot->whenTaken, snapshot->xmin);
 	}
+
+	snapshot->lsn = GetXLogInsertRecPtr();
 }
 
 /*
diff --git a/src/backend/utils/time/snapmgr.c b/src/backend/utils/time/snapmgr.c
@@ -499,6 +499,19 @@ SnapshotSetCommandId(CommandId curcid)
 	/* Should we do the same with CatalogSnapshot? */
 }
 
+/*
+ * GetCurrentSnapshotLSN
+ *		Propagate CommandCounterIncrement into the static snapshots, if set
+ */
+XLogRecPtr
+GetCurrentSnapshotLSN()
+{
+	if (CurrentSnapshot)
+		return CurrentSnapshot->lsn;
+	
+	return InvalidXLogRecPtr;
+}
+
 /*
  * SetTransactionSnapshot
  *		Set the transaction's snapshot from an imported MVCC snapshot.
diff --git a/src/include/utils/snapmgr.h b/src/include/utils/snapmgr.h
@@ -106,6 +106,7 @@ OldSnapshotThresholdActive(void)
 extern Snapshot GetTransactionSnapshot(void);
 extern Snapshot GetLatestSnapshot(void);
 extern void SnapshotSetCommandId(CommandId curcid);
+extern XLogRecPtr GetCurrentSnapshotLSN();
 extern Snapshot GetOldestSnapshot(void);
 
 extern Snapshot GetCatalogSnapshot(Oid relid);

Original file line number	Diff line number	Diff line change
`@@ -2095,7 +2095,6 @@ GetSnapshotDataInitOldSnapshot(Snapshot snapshot)`
`2095`	`2095`	`* If not using "snapshot too old" feature, fill related fields with`
`2096`	`2096`	`* dummy values that don't require any locking.`
`2097`	`2097`	`*/`
`2098`		`- snapshot->lsn = InvalidXLogRecPtr;`
`2099`	`2098`	`snapshot->whenTaken = 0;`
`2100`	`2099`	`}`
`2101`	`2100`	`else`
`@@ -2105,10 +2104,11 @@ GetSnapshotDataInitOldSnapshot(Snapshot snapshot)`
`2105`	`2104`	`* snapshot becomes old enough to need to fall back on the special`
`2106`	`2105`	`* "old snapshot" logic.`
`2107`	`2106`	`*/`
`2108`		`- snapshot->lsn = GetXLogInsertRecPtr();`
`2109`	`2107`	`snapshot->whenTaken = GetSnapshotCurrentTimestamp();`
`2110`	`2108`	`MaintainOldSnapshotTimeMapping(snapshot->whenTaken, snapshot->xmin);`
`2111`	`2109`	`}`
	`2110`	`+`
	`2111`	`+ snapshot->lsn = GetXLogInsertRecPtr();`
`2112`	`2112`	`}`
`2113`	`2113`
`2114`	`2114`	`/*`