Ensure that a cursor is scanned under the same scanCommandId it was

originally created with, so that the set of visible tuples does not
change as a result of other activity.  This essentially makes PG cursors
INSENSITIVE per the SQL92 definition.  See bug report of 13-Feb-02.

src/backend/commands/command.c

@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $Header: /cvsroot/pgsql/src/backend/commands/Attic/command.c,v 1.152 2002/01/03 23:19:30 tgl Exp $
+ *	  $Header: /cvsroot/pgsql/src/backend/commands/Attic/command.c,v 1.153 2002/02/14 15:24:06 tgl Exp $
  *
  * NOTES
  *	  The PerformAddAttribute() code, like most of the relation
@@ -103,6 +103,7 @@ PerformPortalFetch(char *name,
 	QueryDesc  *queryDesc;
 	EState	   *estate;
 	MemoryContext oldcontext;
+	CommandId	savedId;
 	bool		temp_desc = false;
 
 	/*
@@ -156,7 +157,7 @@ PerformPortalFetch(char *name,
 	}
 
 	/*
-	 * tell the destination to prepare to receive some tuples.
+	 * Tell the destination to prepare to receive some tuples.
 	 */
 	BeginCommand(name,
 				 queryDesc->operation,
@@ -168,6 +169,14 @@ PerformPortalFetch(char *name,
 				 tag,
 				 queryDesc->dest);
 
+	/*
+	 * Restore the scanCommandId that was current when the cursor was
+	 * opened.  This ensures that we see the same tuples throughout the
+	 * execution of the cursor.
+	 */
+	savedId = GetScanCommandId();
+	SetScanCommandId(PortalGetCommandId(portal));
+
 	/*
 	 * Determine which direction to go in, and check to see if we're
 	 * already at the end of the available tuples in that direction.  If
@@ -214,6 +223,11 @@ PerformPortalFetch(char *name,
 		}
 	}
 
+	/*
+	 * Restore outer command ID.
+	 */
+	SetScanCommandId(savedId);
+
 	/*
 	 * Clean up and switch back to old context.
 	 */

src/backend/executor/spi.c

@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $Header: /cvsroot/pgsql/src/backend/executor/spi.c,v 1.64 2002/01/03 20:30:47 tgl Exp $
+ *	  $Header: /cvsroot/pgsql/src/backend/executor/spi.c,v 1.65 2002/02/14 15:24:08 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -740,9 +740,9 @@ SPI_cursor_open(char *name, void *plan, Datum *Values, char *Nulls)
 	_SPI_current->processed = 0;
 	_SPI_current->tuptable = NULL;
 
-	/* Make up a portal name if none given */
 	if (name == NULL)
 	{
+		/* Make up a portal name if none given */
 		for (;;)
 		{
 			unnamed_portal_count++;
@@ -755,11 +755,13 @@ SPI_cursor_open(char *name, void *plan, Datum *Values, char *Nulls)
 
 		name = portalname;
 	}
-
-	/* Ensure the portal doesn't exist already */
-	portal = GetPortalByName(name);
-	if (portal != NULL)
-		elog(ERROR, "cursor \"%s\" already in use", name);
+	else
+	{
+		/* Ensure the portal doesn't exist already */
+		portal = GetPortalByName(name);
+		if (portal != NULL)
+			elog(ERROR, "cursor \"%s\" already in use", name);
+	}
 
 	/* Create the portal */
 	portal = CreatePortal(name);
@@ -1228,6 +1230,7 @@ _SPI_cursor_operation(Portal portal, bool forward, int count,
 	QueryDesc  *querydesc;
 	EState	   *estate;
 	MemoryContext oldcontext;
+	CommandId	savedId;
 	CommandDest olddest;
 
 	/* Check that the portal is valid */
@@ -1245,6 +1248,7 @@ _SPI_cursor_operation(Portal portal, bool forward, int count,
 
 	/* Switch to the portals memory context */
 	oldcontext = MemoryContextSwitchTo(PortalGetHeapMemory(portal));
+
 	querydesc = PortalGetQueryDesc(portal);
 	estate = PortalGetState(portal);
 
@@ -1253,6 +1257,14 @@ _SPI_cursor_operation(Portal portal, bool forward, int count,
 	olddest = querydesc->dest;
 	querydesc->dest = dest;
 
+	/*
+	 * Restore the scanCommandId that was current when the cursor was
+	 * opened.  This ensures that we see the same tuples throughout the
+	 * execution of the cursor.
+	 */
+	savedId = GetScanCommandId();
+	SetScanCommandId(PortalGetCommandId(portal));
+
 	/* Run the executor like PerformPortalFetch and remember states */
 	if (forward)
 	{
@@ -1279,6 +1291,11 @@ _SPI_cursor_operation(Portal portal, bool forward, int count,
 		}
 	}
 
+	/*
+	 * Restore outer command ID.
+	 */
+	SetScanCommandId(savedId);
+
 	/* Restore the old command destination and switch back to callers */
 	/* memory context */
 	querydesc->dest = olddest;

src/backend/utils/mmgr/portalmem.c

@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $Header: /cvsroot/pgsql/src/backend/utils/mmgr/portalmem.c,v 1.44 2001/10/25 05:49:51 momjian Exp $
+ *	  $Header: /cvsroot/pgsql/src/backend/utils/mmgr/portalmem.c,v 1.45 2002/02/14 15:24:09 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -168,6 +168,7 @@ PortalSetQuery(Portal portal,
 
 	portal->queryDesc = queryDesc;
 	portal->attinfo = attinfo;
+	portal->commandId = GetScanCommandId();
 	portal->state = state;
 	portal->atStart = true;		/* Allow fetch forward only */
 	portal->atEnd = false;
@@ -213,6 +214,7 @@ CreatePortal(char *name)
 	/* initialize portal query */
 	portal->queryDesc = NULL;
 	portal->attinfo = NULL;
+	portal->commandId = 0;
 	portal->state = NULL;
 	portal->atStart = true;		/* disallow fetches until query is set */
 	portal->atEnd = true;

src/include/utils/portal.h

@@ -7,7 +7,7 @@
  * Portions Copyright (c) 1996-2001, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
- * $Id: portal.h,v 1.31 2001/11/05 17:46:36 momjian Exp $
+ * $Id: portal.h,v 1.32 2002/02/14 15:24:10 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -31,6 +31,7 @@ typedef struct PortalData
 	MemoryContext heap;			/* subsidiary memory */
 	QueryDesc  *queryDesc;		/* Info about query associated with portal */
 	TupleDesc	attinfo;
+	CommandId	commandId;		/* Command counter value for query */
 	EState	   *state;			/* Execution state of query */
 	bool		atStart;		/* T => fetch backwards is not allowed */
 	bool		atEnd;			/* T => fetch forwards is not allowed */
@@ -48,8 +49,9 @@ typedef struct PortalData
  */
 #define PortalGetQueryDesc(portal)	((portal)->queryDesc)
 #define PortalGetTupleDesc(portal)	((portal)->attinfo)
-#define PortalGetState(portal)	((portal)->state)
-#define PortalGetHeapMemory(portal)  ((portal)->heap)
+#define PortalGetCommandId(portal)	((portal)->commandId)
+#define PortalGetState(portal)		((portal)->state)
+#define PortalGetHeapMemory(portal)	((portal)->heap)
 
 /*
  * estimate of the maximum number of open portals a user would have,