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.

3 files changed, 9 insertions, 6 deletions

diff --git a/src/include/optimizer/planmain.h b/src/include/optimizer/planmain.h
index acf24bc17e..9a661a5ee8 100644
--- a/src/include/optimizer/planmain.h
+++ b/src/include/optimizer/planmain.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/optimizer/planmain.h,v 1.120 2009/10/12 18:10:51 tgl Exp $
+ * $PostgreSQL: pgsql/src/include/optimizer/planmain.h,v 1.121 2009/10/26 02:26:45 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -68,7 +68,7 @@ extern Group *make_group(PlannerInfo *root, List *tlist, List *qual,
 		   Plan *lefttree);
 extern Plan *materialize_finished_plan(Plan *subplan);
 extern Unique *make_unique(Plan *lefttree, List *distinctList);
-extern LockRows *make_lockrows(Plan *lefttree, List *rowMarks);
+extern LockRows *make_lockrows(Plan *lefttree, List *rowMarks, int epqParam);
 extern Limit *make_limit(Plan *lefttree, Node *limitOffset, Node *limitCount,
 		   int64 offset_est, int64 count_est);
 extern SetOp *make_setop(SetOpCmd cmd, SetOpStrategy strategy, Plan *lefttree,
@@ -77,7 +77,8 @@ extern SetOp *make_setop(SetOpCmd cmd, SetOpStrategy strategy, Plan *lefttree,
 extern Result *make_result(PlannerInfo *root, List *tlist,
 			Node *resconstantqual, Plan *subplan);
 extern ModifyTable *make_modifytable(CmdType operation, List *resultRelations,
-									 List *subplans, List *returningLists);
+									 List *subplans, List *returningLists,
+									 List *rowMarks, int epqParam);
 extern bool is_projection_capable_plan(Plan *plan);
 
 /*
diff --git a/src/include/optimizer/prep.h b/src/include/optimizer/prep.h
index e8dfb1e28f..982635a57d 100644
--- a/src/include/optimizer/prep.h
+++ b/src/include/optimizer/prep.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/optimizer/prep.h,v 1.66 2009/05/12 00:56:05 tgl Exp $
+ * $PostgreSQL: pgsql/src/include/optimizer/prep.h,v 1.67 2009/10/26 02:26:45 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -40,6 +40,8 @@ extern Expr *canonicalize_qual(Expr *qual);
  */
 extern List *preprocess_targetlist(PlannerInfo *root, List *tlist);
 
+extern PlanRowMark *get_plan_rowmark(List *rowmarks, Index rtindex);
+
 /*
  * prototypes for prepunion.c
  */
diff --git a/src/include/optimizer/subselect.h b/src/include/optimizer/subselect.h
index dcae8031c3..954cff69ac 100644
--- a/src/include/optimizer/subselect.h
+++ b/src/include/optimizer/subselect.h
@@ -5,7 +5,7 @@
  * Portions Copyright (c) 1996-2009, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
- * $PostgreSQL: pgsql/src/include/optimizer/subselect.h,v 1.37 2009/06/11 14:49:11 momjian Exp $
+ * $PostgreSQL: pgsql/src/include/optimizer/subselect.h,v 1.38 2009/10/26 02:26:45 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -29,6 +29,6 @@ extern void SS_finalize_plan(PlannerInfo *root, Plan *plan,
 				 bool attach_initplans);
 extern Param *SS_make_initplan_from_plan(PlannerInfo *root, Plan *plan,
 						   Oid resulttype, int32 resulttypmod);
-extern int	SS_assign_worktable_param(PlannerInfo *root);
+extern int	SS_assign_special_param(PlannerInfo *root);
 
 #endif   /* SUBSELECT_H */