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.

2 files changed, 13 insertions, 8 deletions

diff --git a/src/backend/parser/analyze.c b/src/backend/parser/analyze.c
index 6aad2c79a23..5fb1b31688d 100644
--- a/src/backend/parser/analyze.c
+++ b/src/backend/parser/analyze.c
@@ -17,7 +17,7 @@
  * Portions Copyright (c) 1996-2009, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
- *	$PostgreSQL: pgsql/src/backend/parser/analyze.c,v 1.392 2009/10/12 18:10:48 tgl Exp $
+ *	$PostgreSQL: pgsql/src/backend/parser/analyze.c,v 1.393 2009/10/26 02:26:35 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -2007,7 +2007,11 @@ transformExplainStmt(ParseState *pstate, ExplainStmt *stmt)
 }
 
 
-/* exported so planner can check again after rewriting, query pullup, etc */
+/*
+ * Check for features that are not supported together with FOR UPDATE/SHARE.
+ *
+ * exported so planner can check again after rewriting, query pullup, etc
+ */
 void
 CheckSelectLocking(Query *qry)
 {
@@ -2035,6 +2039,10 @@ CheckSelectLocking(Query *qry)
 		ereport(ERROR,
 				(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
 				 errmsg("SELECT FOR UPDATE/SHARE is not allowed with window functions")));
+	if (expression_returns_set((Node *) qry->targetList))
+		ereport(ERROR,
+				(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
+				 errmsg("SELECT FOR UPDATE/SHARE is not allowed with set-returning functions in the target list")));
 }
 
 /*
@@ -2229,7 +2237,7 @@ applyLockingClause(Query *qry, Index rtindex, bool forUpdate, bool noWait)
 	RowMarkClause *rc;
 
 	/* Check for pre-existing entry for same rtindex */
-	if ((rc = get_rowmark(qry, rtindex)) != NULL)
+	if ((rc = get_parse_rowmark(qry, rtindex)) != NULL)
 	{
 		/*
 		 * If the same RTE is specified both FOR UPDATE and FOR SHARE, treat
@@ -2250,11 +2258,8 @@ applyLockingClause(Query *qry, Index rtindex, bool forUpdate, bool noWait)
 	/* Make a new RowMarkClause */
 	rc = makeNode(RowMarkClause);
 	rc->rti = rtindex;
-	rc->prti = rtindex;
-	rc->rowmarkId = 0;			/* not used until plan time */
 	rc->forUpdate = forUpdate;
 	rc->noWait = noWait;
-	rc->isParent = false;
 	qry->rowMarks = lappend(qry->rowMarks, rc);
 }
 
diff --git a/src/backend/parser/parse_relation.c b/src/backend/parser/parse_relation.c
index 4a0a50504bb..1a5f77d272d 100644
--- a/src/backend/parser/parse_relation.c
+++ b/src/backend/parser/parse_relation.c
@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/parser/parse_relation.c,v 1.144 2009/10/21 20:22:38 tgl Exp $
+ *	  $PostgreSQL: pgsql/src/backend/parser/parse_relation.c,v 1.145 2009/10/26 02:26:35 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -2254,7 +2254,7 @@ get_tle_by_resno(List *tlist, AttrNumber resno)
  * Returns NULL if relation is not selected FOR UPDATE/SHARE
  */
 RowMarkClause *
-get_rowmark(Query *qry, Index rtindex)
+get_parse_rowmark(Query *qry, Index rtindex)
 {
 	ListCell   *l;