Don't try to run clauseless index scans on index types that don't support

it.  Per report from Marinos Yannikos.

diff --git a/src/backend/optimizer/path/indxpath.c b/src/backend/optimizer/path/indxpath.c
index 87b25d28a4304cc88e46e382f490104c9f919189..dbabbf1e08b1d1a68685487ea051602b434f392e 100644 (file)
--- a/src/backend/optimizer/path/indxpath.c
+++ b/src/backend/optimizer/path/indxpath.c
@@ -9,7 +9,7 @@
  *
  *
  * IDENTIFICATION
- *       $Header: /cvsroot/pgsql/src/backend/optimizer/path/indxpath.c,v 1.124.2.1 2003/03/23 01:49:13 tgl Exp $
+ *       $Header: /cvsroot/pgsql/src/backend/optimizer/path/indxpath.c,v 1.124.2.2 2005/04/20 21:48:31 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -188,11 +188,16 @@ create_index_paths(Query *root, RelOptInfo *rel)
                 * 3. Compute pathkeys describing index's ordering, if any, then
                 * see how many of them are actually useful for this query.
                 */
-               index_pathkeys = build_index_pathkeys(root, rel, index,
-                                                                                         ForwardScanDirection);
-               index_is_ordered = (index_pathkeys != NIL);
-               useful_pathkeys = truncate_useless_pathkeys(root, rel,
-                                                                                                       index_pathkeys);
+               index_is_ordered = OidIsValid(index->ordering[0]);
+               if (index_is_ordered)
+               {
+                       index_pathkeys = build_index_pathkeys(root, rel, index,
+                                                                                                 ForwardScanDirection);
+                       useful_pathkeys = truncate_useless_pathkeys(root, rel,
+                                                                                                               index_pathkeys);
+               }
+               else
+                       useful_pathkeys = NIL;
 
                /*
                 * 4. Generate an indexscan path if there are relevant restriction
@@ -202,10 +207,15 @@ create_index_paths(Query *root, RelOptInfo *rel)
                 * If there is a predicate, consider it anyway since the index
                 * predicate has already been found to match the query.  The
                 * selectivity of the predicate might alone make the index useful.
+                *
+                * Note: not all index AMs support scans with no restriction clauses.
+                * We assume here that the AM does so if and only if it supports
+                * ordered scans.  (It would probably be better if there were a
+                * specific flag for this in pg_am, but there's not.)
                 */
                if (restrictclauses != NIL ||
                        useful_pathkeys != NIL ||
-                       index->indpred != NIL)
+                       (index->indpred != NIL && index_is_ordered))
                        add_path(rel, (Path *)
                                         create_index_path(root, rel, index,
                                                                           restrictclauses,