Further tweaking of logic that decides when to materialize an uncorrelated

subplan: do it if subplan has subplans itself, and always do it if the
subplan is an indexscan.  (I originally set it to materialize an indexscan
only if the indexqual is fairly selective, but I dunno what I was
thinking ... an unselective indexscan is still expensive ...)

diff --git a/src/backend/optimizer/plan/subselect.c b/src/backend/optimizer/plan/subselect.c
index eea5b33..a5df56d 100644 (file)
--- a/src/backend/optimizer/plan/subselect.c
+++ b/src/backend/optimizer/plan/subselect.c
@@ -7,7 +7,7 @@
  * Portions Copyright (c) 1994, Regents of the University of California
  *
  * IDENTIFICATION
- *       $Header: /cvsroot/pgsql/src/backend/optimizer/plan/subselect.c,v 1.29 2000/03/02 04:08:16 tgl Exp $
+ *       $Header: /cvsroot/pgsql/src/backend/optimizer/plan/subselect.c,v 1.30 2000/03/11 23:53:41 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -302,8 +302,8 @@ make_subplan(SubLink *slink)
                 * the top of an uncorrelated/undirect correlated subplan, which lets
                 * us do the work of evaluating the subplan only once.  We do this
                 * if the subplan's top plan node is anything more complicated than
-                * a sequential or index scan, and we do it even for those plan types
-                * if the qual appears selective enough to eliminate many tuples.
+                * a plain sequential scan, and we do it even for seqscan if the
+                * qual appears selective enough to eliminate many tuples.
                 */
                if (node->parParam == NIL)
                {
@@ -312,28 +312,19 @@ make_subplan(SubLink *slink)
                        switch (nodeTag(plan))
                        {
                                case T_SeqScan:
-                               {
-                                       Selectivity qualsel;
-
-                                       qualsel = clauselist_selectivity(subquery, plan->qual, 0);
-                                       /* Is 10% selectivity a good threshold?? */
-                                       use_material = qualsel < 0.10;
-                                       break;
-                               }
-                               case T_IndexScan:
-                               {
-                                       List       *indxqual = ((IndexScan *) plan)->indxqualorig;
-                                       Selectivity qualsel;
-
-                                       qualsel = clauselist_selectivity(subquery, plan->qual, 0);
-                                       qualsel *= clauselist_selectivity(subquery, indxqual, 0);
-                                       /* Note: if index is lossy, we just double-counted the
-                                        * index selectivity.  Worth fixing?
-                                        */
-                                       /* Is 10% selectivity a good threshold?? */
-                                       use_material = qualsel < 0.10;
+                                       if (plan->initPlan || plan->subPlan)
+                                               use_material = true;
+                                       else
+                                       {
+                                               Selectivity qualsel;
+
+                                               qualsel = clauselist_selectivity(subquery,
+                                                                                                                plan->qual,
+                                                                                                                0);
+                                               /* Is 10% selectivity a good threshold?? */
+                                               use_material = qualsel < 0.10;
+                                       }
                                        break;
-                               }
                                case T_Material:
                                case T_Sort:
                                        /* Don't add another Material node if there's one already,