sort_inner_and_outer needs a check to ensure that it's consumed all the

mergeclauses in RIGHT/FULL join cases, just like the other routines have.
I'm not quite sure why I thought it didn't need one --- but Nick
Fankhauser's recent bug report proves that it does.

diff --git a/src/backend/optimizer/path/joinpath.c b/src/backend/optimizer/path/joinpath.c
index 15bb567..4d60569 100644 (file)
--- a/src/backend/optimizer/path/joinpath.c
+++ b/src/backend/optimizer/path/joinpath.c
@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *       $Header: /cvsroot/pgsql/src/backend/optimizer/path/joinpath.c,v 1.66 2001/10/25 05:49:32 momjian Exp $
+ *       $Header: /cvsroot/pgsql/src/backend/optimizer/path/joinpath.c,v 1.67 2001/11/11 19:18:54 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -150,10 +150,32 @@ sort_inner_and_outer(Query *root,
                                         List *mergeclause_list,
                                         JoinType jointype)
 {
+       bool            useallclauses;
        List       *all_pathkeys;
        List       *i;
 
        /*
+        * If we are doing a right or full join, we must use *all* the
+        * mergeclauses as join clauses, else we will not have a valid plan.
+        */
+       switch (jointype)
+       {
+               case JOIN_INNER:
+               case JOIN_LEFT:
+                       useallclauses = false;
+                       break;
+               case JOIN_RIGHT:
+               case JOIN_FULL:
+                       useallclauses = true;
+                       break;
+               default:
+                       elog(ERROR, "sort_inner_and_outer: unexpected join type %d",
+                                (int) jointype);
+                       useallclauses = false;  /* keep compiler quiet */
+                       break;
+       }
+
+       /*
         * Each possible ordering of the available mergejoin clauses will
         * generate a differently-sorted result path at essentially the same
         * cost.  We have no basis for choosing one over another at this level
@@ -212,6 +234,11 @@ sort_inner_and_outer(Query *root,
                                                                                                           mergeclause_list);
                Assert(cur_mergeclauses != NIL);
 
+               /* Forget it if can't use all the clauses in right/full join */
+               if (useallclauses &&
+                       length(cur_mergeclauses) != length(mergeclause_list))
+                       continue;
+
                /*
                 * Build sort pathkeys for both sides.
                 *