From: Tom Lane <tgl@sss.pgh.pa.us>
Date: Sun, 23 Jan 2005 02:24:30 +0000 (+0000)
Subject: The result of a FULL or RIGHT join can't be assumed to be sorted by the
X-Git-Tag: REL7_3_9~10
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=48a1dc0d5c2c6a572d1b5e20e1985fa565f90177;p=thirdparty%2Fpostgresql.git

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 8e73bd2f419..55375664fd8 100644
--- 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 1.71 2002/09/04 20:31:20 momjian Exp $
+ *	  $Header: /cvsroot/pgsql/src/backend/optimizer/path/joinpath.c,v 1.71.2.1 2005/01/23 02:24:16 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -253,7 +253,8 @@ 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.  We only consider the cheapest-
@@ -371,7 +372,7 @@ 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 350c761165b..70f4092ed92 100644
--- 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
- *	  $Header: /cvsroot/pgsql/src/backend/optimizer/path/pathkeys.c,v 1.41 2002/09/18 21:35:21 tgl Exp $
+ *	  $Header: /cvsroot/pgsql/src/backend/optimizer/path/pathkeys.c,v 1.41.2.1 2005/01/23 02:24:16 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -623,7 +623,12 @@ find_indexkey_var(Query *root, RelOptInfo *rel, AttrNumber varattno)
  *	  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.
@@ -631,8 +636,12 @@ find_indexkey_var(Query *root, RelOptInfo *rel, AttrNumber varattno)
 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 4222c77ad97..26d9273d327 100644
--- a/src/include/optimizer/paths.h
+++ b/src/include/optimizer/paths.h
@@ -8,7 +8,7 @@
  * Portions Copyright (c) 1996-2002, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
- * $Id: paths.h,v 1.60 2002/06/20 20:29:51 momjian Exp $
+ * $Id: paths.h,v 1.60.2.1 2005/01/23 02:24:30 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -112,6 +112,7 @@ extern List *build_index_pathkeys(Query *root, RelOptInfo *rel,
 					 ScanDirection scandir);
 extern List *build_join_pathkeys(Query *root,
 					RelOptInfo *joinrel,
+					JoinType jointype,
 					List *outer_pathkeys);
 extern List *make_pathkeys_for_sortclauses(List *sortclauses,
 							  List *tlist);