Teach the planner to remove SubqueryScan nodes from the plan if they

aren't doing anything useful (ie, neither selection nor projection).
Also, extend to SubqueryScan the hacks already in place to avoid
unnecessary ExecProject calls when the result would just be the same
tuple the subquery already delivered.  This saves some overhead in
UNION and other set operations, as well as avoiding overhead for
unflatten-able subqueries.  Per example from Sokolov Yura.

1 files changed, 4 insertions, 4 deletions

diff --git a/src/backend/optimizer/plan/planner.c b/src/backend/optimizer/plan/planner.c
index 2e83a7417d..c14983baa0 100644
--- a/src/backend/optimizer/plan/planner.c
+++ b/src/backend/optimizer/plan/planner.c
@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/optimizer/plan/planner.c,v 1.185 2005/04/28 21:47:13 tgl Exp $
+ *	  $PostgreSQL: pgsql/src/backend/optimizer/plan/planner.c,v 1.186 2005/05/22 22:30:19 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -144,12 +144,12 @@ planner(Query *parse, bool isCursor, int cursorOptions,
 			result_plan = materialize_finished_plan(result_plan);
 	}
 
+	/* final cleanup of the plan */
+	result_plan = set_plan_references(result_plan, parse->rtable);
+
 	/* executor wants to know total number of Params used overall */
 	result_plan->nParamExec = list_length(PlannerParamList);
 
-	/* final cleanup of the plan */
-	set_plan_references(result_plan, parse->rtable);
-
 	/* restore state for outer planner, if any */
 	PlannerQueryLevel = save_PlannerQueryLevel;
 	PlannerParamList = save_PlannerParamList;