Re-implement EvalPlanQual processing to improve its performance and eliminate

a lot of strange behaviors that occurred in join cases.  We now identify the
"current" row for every joined relation in UPDATE, DELETE, and SELECT FOR
UPDATE/SHARE queries.  If an EvalPlanQual recheck is necessary, we jam the
appropriate row into each scan node in the rechecking plan, forcing it to emit
only that one row.  The former behavior could rescan the whole of each joined
relation for each recheck, which was terrible for performance, and what's much
worse could result in duplicated output tuples.

Also, the original implementation of EvalPlanQual could not re-use the recheck
execution tree --- it had to go through a full executor init and shutdown for
every row to be tested.  To avoid this overhead, I've associated a special
runtime Param with each LockRows or ModifyTable plan node, and arranged to
make every scan node below such a node depend on that Param.  Thus, by
signaling a change in that Param, the EPQ machinery can just rescan the
already-built test plan.

This patch also adds a prohibition on set-returning functions in the
targetlist of SELECT FOR UPDATE/SHARE.  This is needed to avoid the
duplicate-output-tuple problem.  It seems fairly reasonable since the
other restrictions on SELECT FOR UPDATE are meant to ensure that there
is a unique correspondence between source tuples and result tuples,
which an output SRF destroys as much as anything else does.

1 files changed, 7 insertions, 22 deletions

diff --git a/src/backend/utils/cache/plancache.c b/src/backend/utils/cache/plancache.c
index 6cd138b288c..eb196ebb56a 100644
--- a/src/backend/utils/cache/plancache.c
+++ b/src/backend/utils/cache/plancache.c
@@ -35,7 +35,7 @@
  * Portions Copyright (c) 1994, Regents of the University of California
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/utils/cache/plancache.c,v 1.29 2009/10/10 01:43:50 tgl Exp $
+ *	  $PostgreSQL: pgsql/src/backend/utils/cache/plancache.c,v 1.30 2009/10/26 02:26:41 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -48,6 +48,8 @@
 #include "executor/spi.h"
 #include "nodes/nodeFuncs.h"
 #include "optimizer/planmain.h"
+#include "optimizer/prep.h"
+#include "parser/parsetree.h"
 #include "storage/lmgr.h"
 #include "tcop/pquery.h"
 #include "tcop/tcopprot.h"
@@ -67,7 +69,6 @@ static void AcquireExecutorLocks(List *stmt_list, bool acquire);
 static void AcquirePlannerLocks(List *stmt_list, bool acquire);
 static void ScanQueryForLocks(Query *parsetree, bool acquire);
 static bool ScanQueryWalker(Node *node, bool *acquire);
-static bool rowmark_member(List *rowMarks, int rt_index);
 static bool plan_list_is_transient(List *stmt_list);
 static void PlanCacheRelCallback(Datum arg, Oid relid);
 static void PlanCacheFuncCallback(Datum arg, int cacheid, ItemPointer tuplePtr);
@@ -658,6 +659,7 @@ AcquireExecutorLocks(List *stmt_list, bool acquire)
 		{
 			RangeTblEntry *rte = (RangeTblEntry *) lfirst(lc2);
 			LOCKMODE	lockmode;
+			PlanRowMark *rc;
 
 			rt_index++;
 
@@ -672,7 +674,8 @@ AcquireExecutorLocks(List *stmt_list, bool acquire)
 			 */
 			if (list_member_int(plannedstmt->resultRelations, rt_index))
 				lockmode = RowExclusiveLock;
-			else if (rowmark_member(plannedstmt->rowMarks, rt_index))
+			else if ((rc = get_plan_rowmark(plannedstmt->rowMarks, rt_index)) != NULL &&
+					 RowMarkRequiresRowShareLock(rc->markType))
 				lockmode = RowShareLock;
 			else
 				lockmode = AccessShareLock;
@@ -732,7 +735,7 @@ ScanQueryForLocks(Query *parsetree, bool acquire)
 				/* Acquire or release the appropriate type of lock */
 				if (rt_index == parsetree->resultRelation)
 					lockmode = RowExclusiveLock;
-				else if (rowmark_member(parsetree->rowMarks, rt_index))
+				else if (get_parse_rowmark(parsetree, rt_index) != NULL)
 					lockmode = RowShareLock;
 				else
 					lockmode = AccessShareLock;
@@ -799,24 +802,6 @@ ScanQueryWalker(Node *node, bool *acquire)
 }
 
 /*
- * rowmark_member: check whether an RT index appears in a RowMarkClause list.
- */
-static bool
-rowmark_member(List *rowMarks, int rt_index)
-{
-	ListCell   *l;
-
-	foreach(l, rowMarks)
-	{
-		RowMarkClause *rc = (RowMarkClause *) lfirst(l);
-
-		if (rc->rti == rt_index)
-			return true;
-	}
-	return false;
-}
-
-/*
  * plan_list_is_transient: check if any of the plans in the list are transient.
  */
 static bool