Fix for bug #795: two clauses that seem redundant are not really, if

one is pushed down into an outer join and the other is not.

diff --git a/src/backend/optimizer/util/relnode.c b/src/backend/optimizer/util/relnode.c
index 49e2f1f..a07a208 100644 (file)
--- a/src/backend/optimizer/util/relnode.c
+++ b/src/backend/optimizer/util/relnode.c
@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *       $Header: /cvsroot/pgsql/src/backend/optimizer/util/relnode.c,v 1.39 2002/09/04 20:31:22 momjian Exp $
+ *       $Header: /cvsroot/pgsql/src/backend/optimizer/util/relnode.c,v 1.40 2002/10/12 22:24:49 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -28,7 +28,8 @@ static List *new_join_tlist(List *tlist, int first_resdomno);
 static List *build_joinrel_restrictlist(Query *root,
                                                   RelOptInfo *joinrel,
                                                   RelOptInfo *outer_rel,
-                                                  RelOptInfo *inner_rel);
+                                                  RelOptInfo *inner_rel,
+                                                  JoinType jointype);
 static void build_joinrel_joinlist(RelOptInfo *joinrel,
                                           RelOptInfo *outer_rel,
                                           RelOptInfo *inner_rel);
@@ -334,7 +335,8 @@ build_join_rel(Query *root,
                        *restrictlist_ptr = build_joinrel_restrictlist(root,
                                                                                                                   joinrel,
                                                                                                                   outer_rel,
-                                                                                                                  inner_rel);
+                                                                                                                  inner_rel,
+                                                                                                                  jointype);
                return joinrel;
        }
 
@@ -419,7 +421,8 @@ build_join_rel(Query *root,
        restrictlist = build_joinrel_restrictlist(root,
                                                                                          joinrel,
                                                                                          outer_rel,
-                                                                                         inner_rel);
+                                                                                         inner_rel,
+                                                                                         jointype);
        if (restrictlist_ptr)
                *restrictlist_ptr = restrictlist;
        build_joinrel_joinlist(joinrel, outer_rel, inner_rel);
@@ -508,6 +511,7 @@ new_join_tlist(List *tlist,
  * 'joinrel' is a join relation node
  * 'outer_rel' and 'inner_rel' are a pair of relations that can be joined
  *             to form joinrel.
+ * 'jointype' is the type of join used.
  *
  * build_joinrel_restrictlist() returns a list of relevant restrictinfos,
  * whereas build_joinrel_joinlist() stores its results in the joinrel's
@@ -522,7 +526,8 @@ static List *
 build_joinrel_restrictlist(Query *root,
                                                   RelOptInfo *joinrel,
                                                   RelOptInfo *outer_rel,
-                                                  RelOptInfo *inner_rel)
+                                                  RelOptInfo *inner_rel,
+                                                  JoinType jointype)
 {
        List       *result = NIL;
        List       *rlist;
@@ -553,6 +558,11 @@ build_joinrel_restrictlist(Query *root,
         * one clause that checks equality between any set member on the left
         * and any member on the right; by transitivity, all the rest are then
         * equal.
+        *
+        * Weird special case: if we have two clauses that seem redundant
+        * except one is pushed down into an outer join and the other isn't,
+        * then they're not really redundant, because one constrains the
+        * joined rows after addition of null fill rows, and the other doesn't.
         */
        foreach(item, rlist)
        {
@@ -576,7 +586,9 @@ build_joinrel_restrictlist(Query *root,
 
                                if (oldrinfo->mergejoinoperator != InvalidOid &&
                                        rinfo->left_pathkey == oldrinfo->left_pathkey &&
-                                       rinfo->right_pathkey == oldrinfo->right_pathkey)
+                                       rinfo->right_pathkey == oldrinfo->right_pathkey &&
+                                       (rinfo->ispusheddown == oldrinfo->ispusheddown ||
+                                        !IS_OUTER_JOIN(jointype)))
                                {
                                        redundant = true;
                                        break;