Fix an error in make_outerjoininfo introduced by my patch of 30-Aug: the code

neglected to test whether an outer join's join-condition actually refers to
the lower outer join it is looking at.  (The comment correctly described what
was supposed to happen, but the code didn't do it...)  This often resulted in
adding an unnecessary constraint on the join order of the two outer joins,
which was bad enough.  However, it also seems to expose a performance
problem in an older patch (from 15-Feb): once we've decided that there is a
join ordering constraint, we will start trying clauseless joins between every
combination of rels within the constraint, which pointlessly eats up lots of
time and space if there are numerous rels below the outer join.  That probably
needs to be revisited :-(.  Per gripe from Jakub Ouhrabka.

diff --git a/src/backend/optimizer/plan/initsplan.c b/src/backend/optimizer/plan/initsplan.c
index 70543613fe2949116d060383f807aa6d15df1f48..bacd875abf0bed2fc0127edd762e71479c1b28df 100644 (file)
--- a/src/backend/optimizer/plan/initsplan.c
+++ b/src/backend/optimizer/plan/initsplan.c
@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *       $PostgreSQL: pgsql/src/backend/optimizer/plan/initsplan.c,v 1.134 2007/10/04 20:44:47 tgl Exp $
+ *       $PostgreSQL: pgsql/src/backend/optimizer/plan/initsplan.c,v 1.135 2007/10/24 20:54:27 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -623,6 +623,7 @@ make_outerjoininfo(PlannerInfo *root,
                 * rel in the lower OJ's min_righthand, not its whole syn_righthand.
                 */
                if (bms_overlap(left_rels, otherinfo->syn_righthand) &&
+                       bms_overlap(clause_relids, otherinfo->syn_righthand) &&
                        !bms_overlap(strict_relids, otherinfo->min_righthand))
                {
                        min_lefthand = bms_add_members(min_lefthand,