Test for whether a previous IN join restricts the current join was too

strict, per discussion with Dennis Haney.
Also, rearrange the preceding tests to avoid redundancy.

diff --git a/src/backend/optimizer/path/joinrels.c b/src/backend/optimizer/path/joinrels.c
index 50b9aef0110673ea83df0ddd1c9609ddcf85c84a..07caab48ac682e3498b9960661d01c6041127b97 100644 (file)
--- a/src/backend/optimizer/path/joinrels.c
+++ b/src/backend/optimizer/path/joinrels.c
@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *   $PostgreSQL: pgsql/src/backend/optimizer/path/joinrels.c,v 1.66 2004/01/24 00:37:28 tgl Exp $
+ *   $PostgreSQL: pgsql/src/backend/optimizer/path/joinrels.c,v 1.67 2004/03/08 17:20:17 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -483,35 +483,45 @@ make_join_rel(Query *root, RelOptInfo *rel1, RelOptInfo *rel2,
            InClauseInfo *ininfo = (InClauseInfo *) lfirst(l);
 
            /*
-            * Cannot join if proposed join contains part, but only part,
-            * of the RHS, *and* it contains rels not in the RHS.
+            * This IN clause is not relevant unless its RHS overlaps the
+            * proposed join.  (Check this first as a fast path for dismissing
+            * most irrelevant INs quickly.)
             */
-           if (bms_overlap(ininfo->righthand, joinrelids) &&
-               !bms_is_subset(ininfo->righthand, joinrelids) &&
-               !bms_is_subset(joinrelids, ininfo->righthand))
-           {
-               bms_free(joinrelids);
-               return NULL;
-           }
+           if (!bms_overlap(ininfo->righthand, joinrelids))
+               continue;
 
            /*
-            * No issue unless we are looking at a join of the IN's RHS to
-            * other stuff.
+            * If we are still building the IN clause's RHS, then this IN
+            * clause isn't relevant yet.
             */
-           if (!(bms_is_subset(ininfo->righthand, joinrelids) &&
-                 !bms_equal(ininfo->righthand, joinrelids)))
+           if (bms_is_subset(joinrelids, ininfo->righthand))
                continue;
 
            /*
-            * If we already joined IN's RHS to any part of its LHS in
-            * either input path, then this join is not constrained (the
-            * necessary work was done at a lower level).
+            * Cannot join if proposed join contains rels not in the RHS
+            * *and* contains only part of the RHS.  We must build the
+            * complete RHS (subselect's join) before it can be joined to
+            * rels outside the subselect.
+            */
+           if (!bms_is_subset(ininfo->righthand, joinrelids))
+           {
+               bms_free(joinrelids);
+               return NULL;
+           }
+
+           /*
+            * At this point we are considering a join of the IN's RHS to
+            * some other rel(s).
+            *
+            * If we already joined IN's RHS to any other rels in either
+            * input path, then this join is not constrained (the necessary
+            * work was done at the lower level where that join occurred).
             */
-           if (bms_overlap(ininfo->lefthand, rel1->relids) &&
-               bms_is_subset(ininfo->righthand, rel1->relids))
+           if (bms_is_subset(ininfo->righthand, rel1->relids) &&
+               !bms_equal(ininfo->righthand, rel1->relids))
                continue;
-           if (bms_overlap(ininfo->lefthand, rel2->relids) &&
-               bms_is_subset(ininfo->righthand, rel2->relids))
+           if (bms_is_subset(ininfo->righthand, rel2->relids) &&
+               !bms_equal(ininfo->righthand, rel2->relids))
                continue;
 
            /*