The result of a FULL or RIGHT join can't be assumed to be sorted by the

left input's sorting, because null rows may be inserted at various points.
Per report from Ferenc Lutischá¸n.

diff --git a/src/backend/optimizer/path/joinpath.c b/src/backend/optimizer/path/joinpath.c
index 65c7690af474e1c41257cde2330dd1a8c94fe23d..97e4d7dda87ebf5f594a44203c5fc16e5640f00b 100644 (file)
--- a/src/backend/optimizer/path/joinpath.c
+++ b/src/backend/optimizer/path/joinpath.c
@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *       $PostgreSQL: pgsql/src/backend/optimizer/path/joinpath.c,v 1.91 2004/12/31 22:00:04 pgsql Exp $
+ *       $PostgreSQL: pgsql/src/backend/optimizer/path/joinpath.c,v 1.92 2005/01/23 02:21:26 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -271,7 +271,8 @@ sort_inner_and_outer(Query *root,
                                                                                                   cur_mergeclauses,
                                                                                                   innerrel);
                /* Build pathkeys representing output sort order. */
-               merge_pathkeys = build_join_pathkeys(root, joinrel, outerkeys);
+               merge_pathkeys = build_join_pathkeys(root, joinrel, jointype,
+                                                                                        outerkeys);
 
                /*
                 * And now we can make the path.
@@ -431,7 +432,7 @@ match_unsorted_outer(Query *root,
                 * as a nestloop, and even if some of the mergeclauses are
                 * implemented by qpquals rather than as true mergeclauses):
                 */
-               merge_pathkeys = build_join_pathkeys(root, joinrel,
+               merge_pathkeys = build_join_pathkeys(root, joinrel, jointype,
                                                                                         outerpath->pathkeys);
 
                if (nestjoinOK)

diff --git a/src/backend/optimizer/path/pathkeys.c b/src/backend/optimizer/path/pathkeys.c
index e10a41b95181a8a11ad5f1706d0c0eb99c148bfa..d2c6de54dd7979a6d4779db3d216e1dd82cf0c80 100644 (file)
--- a/src/backend/optimizer/path/pathkeys.c
+++ b/src/backend/optimizer/path/pathkeys.c
@@ -11,7 +11,7 @@
  * Portions Copyright (c) 1994, Regents of the University of California
  *
  * IDENTIFICATION
- *       $PostgreSQL: pgsql/src/backend/optimizer/path/pathkeys.c,v 1.63 2004/12/31 22:00:04 pgsql Exp $
+ *       $PostgreSQL: pgsql/src/backend/optimizer/path/pathkeys.c,v 1.64 2005/01/23 02:21:26 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -858,7 +858,12 @@ build_subquery_pathkeys(Query *root, RelOptInfo *rel, Query *subquery)
  *       vars they were joined with; furthermore, it doesn't matter what kind
  *       of join algorithm is actually used.
  *
+ *       EXCEPTION: in a FULL or RIGHT join, we cannot treat the result as
+ *       having the outer path's path keys, because null lefthand rows may be
+ *       inserted at random points.  It must be treated as unsorted.
+ *
  * 'joinrel' is the join relation that paths are being formed for
+ * 'jointype' is the join type (inner, left, full, etc)
  * 'outer_pathkeys' is the list of the current outer path's path keys
  *
  * Returns the list of new path keys.
@@ -866,8 +871,12 @@ build_subquery_pathkeys(Query *root, RelOptInfo *rel, Query *subquery)
 List *
 build_join_pathkeys(Query *root,
                                        RelOptInfo *joinrel,
+                                       JoinType jointype,
                                        List *outer_pathkeys)
 {
+       if (jointype == JOIN_FULL || jointype == JOIN_RIGHT)
+               return NIL;
+
        /*
         * This used to be quite a complex bit of code, but now that all
         * pathkey sublists start out life canonicalized, we don't have to do

diff --git a/src/include/optimizer/paths.h b/src/include/optimizer/paths.h
index 97644f3cfcd75934681a6fbcef03ef0dd54fe31f..db1a9f4affcf14b9c7aa523257ebbe631da24587 100644 (file)
--- a/src/include/optimizer/paths.h
+++ b/src/include/optimizer/paths.h
@@ -8,7 +8,7 @@
  * Portions Copyright (c) 1996-2005, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
- * $PostgreSQL: pgsql/src/include/optimizer/paths.h,v 1.77 2004/12/31 22:03:36 pgsql Exp $
+ * $PostgreSQL: pgsql/src/include/optimizer/paths.h,v 1.78 2005/01/23 02:21:36 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -114,6 +114,7 @@ extern List *build_subquery_pathkeys(Query *root, RelOptInfo *rel,
                                                Query *subquery);
 extern List *build_join_pathkeys(Query *root,
                                        RelOptInfo *joinrel,
+                                       JoinType jointype,
                                        List *outer_pathkeys);
 extern List *make_pathkeys_for_sortclauses(List *sortclauses,
                                                          List *tlist);