Get rid of ReferentialIntegritySnapshotOverride by extending Executor API

to allow es_snapshot to be set to SnapshotNow rather than a query snapshot.
This solves a bug reported by Wade Klaver, wherein triggers fired as a
result of RI cascade updates could misbehave.

Author: tglsfdc

src/backend/commands/explain.c

@@ -7,7 +7,7 @@
  * Portions Copyright (c) 1994-5, Regents of the University of California
  *
  * IDENTIFICATION
- *	  $Header: /cvsroot/pgsql/src/backend/commands/explain.c,v 1.115 2003/08/11 20:46:46 tgl Exp $
+ *	  $Header: /cvsroot/pgsql/src/backend/commands/explain.c,v 1.116 2003/09/25 18:58:35 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -207,7 +207,7 @@ ExplainOnePlan(QueryDesc *queryDesc, ExplainStmt *stmt,
 	gettimeofday(&starttime, NULL);
 
 	/* call ExecutorStart to prepare the plan for execution */
-	ExecutorStart(queryDesc, !stmt->analyze);
+	ExecutorStart(queryDesc, false, !stmt->analyze);
 
 	/* Execute the plan for statistics if asked for */
 	if (stmt->analyze)

src/backend/commands/trigger.c

@@ -7,7 +7,7 @@
  * Portions Copyright (c) 1994, Regents of the University of California
  *
  * IDENTIFICATION
- *	  $Header: /cvsroot/pgsql/src/backend/commands/trigger.c,v 1.157 2003/09/25 06:57:58 petere Exp $
+ *	  $Header: /cvsroot/pgsql/src/backend/commands/trigger.c,v 1.158 2003/09/25 18:58:35 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -1862,12 +1862,6 @@ DeferredTriggerExecute(DeferredTriggerEvent event, int itemno,
 	if (rettuple != NULL && rettuple != &oldtuple && rettuple != &newtuple)
 		heap_freetuple(rettuple);
 
-	/*
-	 * Might have been a referential integrity constraint trigger. Reset
-	 * the snapshot overriding flag.
-	 */
-	ReferentialIntegritySnapshotOverride = false;
-
 	/*
 	 * Release buffers
 	 */

src/backend/executor/execMain.c

@@ -26,7 +26,7 @@
  *
  *
  * IDENTIFICATION
- *	  $Header: /cvsroot/pgsql/src/backend/executor/execMain.c,v 1.218 2003/09/25 06:57:59 petere Exp $
+ *	  $Header: /cvsroot/pgsql/src/backend/executor/execMain.c,v 1.219 2003/09/25 18:58:35 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -104,6 +104,9 @@ static void EvalPlanQualStop(evalPlanQual *epq);
  * field of the QueryDesc is filled in to describe the tuples that will be
  * returned, and the internal fields (estate and planstate) are set up.
  *
+ * If useSnapshotNow is true, run the query with SnapshotNow time qual rules
+ * instead of the normal use of QuerySnapshot.
+ *
  * If explainOnly is true, we are not actually intending to run the plan,
  * only to set up for EXPLAIN; so skip unwanted side-effects.
  *
@@ -112,7 +115,7 @@ static void EvalPlanQualStop(evalPlanQual *epq);
  * ----------------------------------------------------------------
  */
 void
-ExecutorStart(QueryDesc *queryDesc, bool explainOnly)
+ExecutorStart(QueryDesc *queryDesc, bool useSnapshotNow, bool explainOnly)
 {
 	EState	   *estate;
 	MemoryContext oldcontext;
@@ -154,7 +157,16 @@ ExecutorStart(QueryDesc *queryDesc, bool explainOnly)
 	 * the life of this query, even if it outlives the current command and
 	 * current snapshot.
 	 */
-	estate->es_snapshot = CopyQuerySnapshot();
+	if (useSnapshotNow)
+	{
+		estate->es_snapshot = SnapshotNow;
+		estate->es_snapshot_cid = GetCurrentCommandId();
+	}
+	else
+	{
+		estate->es_snapshot = CopyQuerySnapshot();
+		estate->es_snapshot_cid = estate->es_snapshot->curcid;
+	}
 
 	/*
 	 * Initialize the plan state tree
@@ -1106,7 +1118,7 @@ lnext:	;
 
 					tuple.t_self = *((ItemPointer) DatumGetPointer(datum));
 					test = heap_mark4update(erm->relation, &tuple, &buffer,
-											estate->es_snapshot->curcid);
+											estate->es_snapshot_cid);
 					ReleaseBuffer(buffer);
 					switch (test)
 					{
@@ -1266,7 +1278,7 @@ ExecSelect(TupleTableSlot *slot,
 	if (estate->es_into_relation_descriptor != NULL)
 	{
 		heap_insert(estate->es_into_relation_descriptor, tuple,
-					estate->es_snapshot->curcid);
+					estate->es_snapshot_cid);
 		IncrAppended();
 	}
 
@@ -1342,7 +1354,7 @@ ExecInsert(TupleTableSlot *slot,
 	 * insert the tuple
 	 */
 	newId = heap_insert(resultRelationDesc, tuple,
-						estate->es_snapshot->curcid);
+						estate->es_snapshot_cid);
 
 	IncrAppended();
 	(estate->es_processed)++;
@@ -1394,7 +1406,7 @@ ExecDelete(TupleTableSlot *slot,
 		bool		dodelete;
 
 		dodelete = ExecBRDeleteTriggers(estate, resultRelInfo, tupleid,
-										estate->es_snapshot->curcid);
+										estate->es_snapshot_cid);
 
 		if (!dodelete)			/* "do nothing" */
 			return;
@@ -1406,7 +1418,7 @@ ExecDelete(TupleTableSlot *slot,
 ldelete:;
 	result = heap_delete(resultRelationDesc, tupleid,
 						 &ctid,
-						 estate->es_snapshot->curcid,
+						 estate->es_snapshot_cid,
 						 true /* wait for commit */);
 	switch (result)
 	{
@@ -1505,7 +1517,7 @@ ExecUpdate(TupleTableSlot *slot,
 
 		newtuple = ExecBRUpdateTriggers(estate, resultRelInfo,
 										tupleid, tuple,
-										estate->es_snapshot->curcid);
+										estate->es_snapshot_cid);
 
 		if (newtuple == NULL)	/* "do nothing" */
 			return;
@@ -1541,7 +1553,7 @@ lreplace:;
 	 */
 	result = heap_update(resultRelationDesc, tupleid, tuple,
 						 &ctid,
-						 estate->es_snapshot->curcid,
+						 estate->es_snapshot_cid,
 						 true /* wait for commit */);
 	switch (result)
 	{
@@ -2027,6 +2039,7 @@ EvalPlanQualStart(evalPlanQual *epq, EState *estate, evalPlanQual *priorepq)
 	 */
 	epqstate->es_direction = ForwardScanDirection;
 	epqstate->es_snapshot = estate->es_snapshot;
+	epqstate->es_snapshot_cid = estate->es_snapshot_cid;
 	epqstate->es_range_table = estate->es_range_table;
 	epqstate->es_result_relations = estate->es_result_relations;
 	epqstate->es_num_result_relations = estate->es_num_result_relations;

src/backend/executor/execUtils.c

@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $Header: /cvsroot/pgsql/src/backend/executor/execUtils.c,v 1.104 2003/09/24 18:54:01 tgl Exp $
+ *	  $Header: /cvsroot/pgsql/src/backend/executor/execUtils.c,v 1.105 2003/09/25 18:58:35 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -178,6 +178,7 @@ CreateExecutorState(void)
 	 */
 	estate->es_direction = ForwardScanDirection;
 	estate->es_snapshot = SnapshotNow;
+	estate->es_snapshot_cid = FirstCommandId;
 	estate->es_range_table = NIL;
 
 	estate->es_result_relations = NULL;

src/backend/executor/functions.c

@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $Header: /cvsroot/pgsql/src/backend/executor/functions.c,v 1.74 2003/09/25 06:57:59 petere Exp $
+ *	  $Header: /cvsroot/pgsql/src/backend/executor/functions.c,v 1.75 2003/09/25 18:58:35 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -291,7 +291,7 @@ postquel_start(execution_state *es, SQLFunctionCachePtr fcache)
 
 	/* Utility commands don't need Executor. */
 	if (es->qd->operation != CMD_UTILITY)
-		ExecutorStart(es->qd, false);
+		ExecutorStart(es->qd, false, false);
 
 	es->status = F_EXEC_RUN;
 }

src/backend/executor/nodeSubplan.c

@@ -7,7 +7,7 @@
  * Portions Copyright (c) 1994, Regents of the University of California
  *
  * IDENTIFICATION
- *	  $Header: /cvsroot/pgsql/src/backend/executor/nodeSubplan.c,v 1.56 2003/09/25 06:57:59 petere Exp $
+ *	  $Header: /cvsroot/pgsql/src/backend/executor/nodeSubplan.c,v 1.57 2003/09/25 18:58:35 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -709,6 +709,7 @@ ExecInitSubPlan(SubPlanState *node, EState *estate)
 	sp_estate->es_tupleTable =
 		ExecCreateTupleTable(ExecCountSlotsNode(subplan->plan) + 10);
 	sp_estate->es_snapshot = estate->es_snapshot;
+	sp_estate->es_snapshot_cid = estate->es_snapshot_cid;
 	sp_estate->es_instrument = estate->es_instrument;
 
 	/*

src/backend/executor/nodeSubqueryscan.c

@@ -12,7 +12,7 @@
  *
  *
  * IDENTIFICATION
- *	  $Header: /cvsroot/pgsql/src/backend/executor/nodeSubqueryscan.c,v 1.20 2003/08/04 02:39:59 momjian Exp $
+ *	  $Header: /cvsroot/pgsql/src/backend/executor/nodeSubqueryscan.c,v 1.21 2003/09/25 18:58:35 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -177,6 +177,7 @@ ExecInitSubqueryScan(SubqueryScan *node, EState *estate)
 	sp_estate->es_tupleTable =
 		ExecCreateTupleTable(ExecCountSlotsNode(node->subplan) + 10);
 	sp_estate->es_snapshot = estate->es_snapshot;
+	sp_estate->es_snapshot_cid = estate->es_snapshot_cid;
 	sp_estate->es_instrument = estate->es_instrument;
 
 	/*

src/backend/executor/spi.c

@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $Header: /cvsroot/pgsql/src/backend/executor/spi.c,v 1.105 2003/09/23 15:11:33 tgl Exp $
+ *	  $Header: /cvsroot/pgsql/src/backend/executor/spi.c,v 1.106 2003/09/25 18:58:35 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -32,10 +32,12 @@ static int	_SPI_connected = -1;
 static int	_SPI_curid = -1;
 
 static int	_SPI_execute(const char *src, int tcount, _SPI_plan *plan);
-static int	_SPI_pquery(QueryDesc *queryDesc, bool runit, int tcount);
+static int	_SPI_pquery(QueryDesc *queryDesc, bool runit,
+						bool useSnapshotNow, int tcount);
 
 static int _SPI_execute_plan(_SPI_plan *plan,
-				  Datum *Values, const char *Nulls, int tcount);
+							 Datum *Values, const char *Nulls,
+							 bool useSnapshotNow, int tcount);
 
 static void _SPI_cursor_operation(Portal portal, bool forward, int count,
 					  DestReceiver *dest);
@@ -236,7 +238,33 @@ SPI_execp(void *plan, Datum *Values, const char *Nulls, int tcount)
 	if (res < 0)
 		return res;
 
-	res = _SPI_execute_plan((_SPI_plan *) plan, Values, Nulls, tcount);
+	res = _SPI_execute_plan((_SPI_plan *) plan, Values, Nulls, false, tcount);
+
+	_SPI_end_call(true);
+	return res;
+}
+
+/*
+ * SPI_execp_now -- identical to SPI_execp, except that we use SnapshotNow
+ * instead of the normal QuerySnapshot.  This is currently not documented
+ * in spi.sgml because it is only intended for use by RI triggers.
+ */
+int
+SPI_execp_now(void *plan, Datum *Values, const char *Nulls, int tcount)
+{
+	int			res;
+
+	if (plan == NULL || tcount < 0)
+		return SPI_ERROR_ARGUMENT;
+
+	if (((_SPI_plan *) plan)->nargs > 0 && Values == NULL)
+		return SPI_ERROR_PARAM;
+
+	res = _SPI_begin_call(true);
+	if (res < 0)
+		return res;
+
+	res = _SPI_execute_plan((_SPI_plan *) plan, Values, Nulls, true, tcount);
 
 	_SPI_end_call(true);
 	return res;
@@ -1068,7 +1096,7 @@ _SPI_execute(const char *src, int tcount, _SPI_plan *plan)
 			{
 				qdesc = CreateQueryDesc(queryTree, planTree, dest,
 										NULL, false);
-				res = _SPI_pquery(qdesc, true,
+				res = _SPI_pquery(qdesc, true, false,
 								  queryTree->canSetTag ? tcount : 0);
 				if (res < 0)
 					return res;
@@ -1078,7 +1106,7 @@ _SPI_execute(const char *src, int tcount, _SPI_plan *plan)
 			{
 				qdesc = CreateQueryDesc(queryTree, planTree, dest,
 										NULL, false);
-				res = _SPI_pquery(qdesc, false, 0);
+				res = _SPI_pquery(qdesc, false, false, 0);
 				if (res < 0)
 					return res;
 			}
@@ -1096,7 +1124,7 @@ _SPI_execute(const char *src, int tcount, _SPI_plan *plan)
 
 static int
 _SPI_execute_plan(_SPI_plan *plan, Datum *Values, const char *Nulls,
-				  int tcount)
+				  bool useSnapshotNow, int tcount)
 {
 	List	   *query_list_list = plan->qtlist;
 	List	   *plan_list = plan->ptlist;
@@ -1167,7 +1195,7 @@ _SPI_execute_plan(_SPI_plan *plan, Datum *Values, const char *Nulls,
 			{
 				qdesc = CreateQueryDesc(queryTree, planTree, dest,
 										paramLI, false);
-				res = _SPI_pquery(qdesc, true,
+				res = _SPI_pquery(qdesc, true, useSnapshotNow,
 								  queryTree->canSetTag ? tcount : 0);
 				if (res < 0)
 					return res;
@@ -1180,7 +1208,7 @@ _SPI_execute_plan(_SPI_plan *plan, Datum *Values, const char *Nulls,
 }
 
 static int
-_SPI_pquery(QueryDesc *queryDesc, bool runit, int tcount)
+_SPI_pquery(QueryDesc *queryDesc, bool runit, bool useSnapshotNow, int tcount)
 {
 	int			operation = queryDesc->operation;
 	int			res;
@@ -1217,7 +1245,7 @@ _SPI_pquery(QueryDesc *queryDesc, bool runit, int tcount)
 		ResetUsage();
 #endif
 
-	ExecutorStart(queryDesc, false);
+	ExecutorStart(queryDesc, useSnapshotNow, false);
 
 	ExecutorRun(queryDesc, ForwardScanDirection, (long) tcount);
 

src/backend/tcop/pquery.c

@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $Header: /cvsroot/pgsql/src/backend/tcop/pquery.c,v 1.72 2003/08/12 18:23:21 tgl Exp $
+ *	  $Header: /cvsroot/pgsql/src/backend/tcop/pquery.c,v 1.73 2003/09/25 18:58:35 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -131,7 +131,7 @@ ProcessQuery(Query *parsetree,
 	/*
 	 * Call ExecStart to prepare the plan for execution
 	 */
-	ExecutorStart(queryDesc, false);
+	ExecutorStart(queryDesc, false, false);
 
 	/*
 	 * Run the plan to completion.
@@ -269,7 +269,7 @@ PortalStart(Portal portal, ParamListInfo params)
 			/*
 			 * Call ExecStart to prepare the plan for execution
 			 */
-			ExecutorStart(queryDesc, false);
+			ExecutorStart(queryDesc, false, false);
 
 			/*
 			 * This tells PortalCleanup to shut down the executor