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, 21 insertions, 11 deletions

diff --git a/src/include/executor/executor.h b/src/include/executor/executor.h
index 36e7d35467f..ba2f42d6862 100644
--- a/src/include/executor/executor.h
+++ b/src/include/executor/executor.h
@@ -7,7 +7,7 @@
  * Portions Copyright (c) 1996-2009, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
- * $PostgreSQL: pgsql/src/include/executor/executor.h,v 1.162 2009/10/12 18:10:51 tgl Exp $
+ * $PostgreSQL: pgsql/src/include/executor/executor.h,v 1.163 2009/10/26 02:26:41 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -166,16 +166,23 @@ extern ResultRelInfo *ExecGetTriggerResultRel(EState *estate, Oid relid);
 extern bool ExecContextForcesOids(PlanState *planstate, bool *hasoids);
 extern void ExecConstraints(ResultRelInfo *resultRelInfo,
 				TupleTableSlot *slot, EState *estate);
-extern TupleTableSlot *EvalPlanQual(EState *estate, Index rti,
-			 PlanState *subplanstate,
+extern TupleTableSlot *EvalPlanQual(EState *estate, EPQState *epqstate,
+			 Relation relation, Index rti,
 			 ItemPointer tid, TransactionId priorXmax);
-extern HeapTuple EvalPlanQualFetch(EState *estate, Index rti,
-				  ItemPointer tid, TransactionId priorXmax);
-extern void EvalPlanQualPush(EState *estate, Index rti,
-							 PlanState *subplanstate);
-extern void EvalPlanQualSetTuple(EState *estate, Index rti, HeapTuple tuple);
-extern TupleTableSlot *EvalPlanQualNext(EState *estate);
-extern void EvalPlanQualPop(EState *estate, PlanState *subplanstate);
+extern HeapTuple EvalPlanQualFetch(EState *estate, Relation relation,
+				  int lockmode, ItemPointer tid, TransactionId priorXmax);
+extern void EvalPlanQualInit(EPQState *epqstate, EState *estate,
+							 Plan *subplan, int epqParam);
+extern void EvalPlanQualSetPlan(EPQState *epqstate, Plan *subplan);
+extern void EvalPlanQualAddRowMark(EPQState *epqstate, ExecRowMark *erm);
+extern void EvalPlanQualSetTuple(EPQState *epqstate, Index rti,
+								 HeapTuple tuple);
+extern HeapTuple EvalPlanQualGetTuple(EPQState *epqstate, Index rti);
+#define EvalPlanQualSetSlot(epqstate, slot)  ((epqstate)->origslot = (slot))
+extern void EvalPlanQualFetchRowMarks(EPQState *epqstate);
+extern TupleTableSlot *EvalPlanQualNext(EPQState *epqstate);
+extern void EvalPlanQualBegin(EPQState *epqstate, EState *parentestate);
+extern void EvalPlanQualEnd(EPQState *epqstate);
 extern DestReceiver *CreateIntoRelDestReceiver(void);
 
 /*
@@ -211,9 +218,12 @@ extern TupleTableSlot *ExecProject(ProjectionInfo *projInfo,
  * prototypes from functions in execScan.c
  */
 typedef TupleTableSlot *(*ExecScanAccessMtd) (ScanState *node);
+typedef bool (*ExecScanRecheckMtd) (ScanState *node, TupleTableSlot *slot);
 
-extern TupleTableSlot *ExecScan(ScanState *node, ExecScanAccessMtd accessMtd);
+extern TupleTableSlot *ExecScan(ScanState *node, ExecScanAccessMtd accessMtd,
+								ExecScanRecheckMtd recheckMtd);
 extern void ExecAssignScanProjectionInfo(ScanState *node);
+extern void ExecScanReScan(ScanState *node);
 
 /*
  * prototypes from functions in execTuples.c