Repair two constraint-exclusion corner cases triggered by proving that an

[postgresql] / src / backend / optimizer / path / allpaths.c

diff --git a/src/backend/optimizer/path/allpaths.c b/src/backend/optimizer/path/allpaths.c
index 07a99e9c6b7c6503542e1346cce33ef2377aefa9..0ad3dc5aae1b4c0f32107b20fe62ffc7a825c533 100644 (file)
--- a/src/backend/optimizer/path/allpaths.c
+++ b/src/backend/optimizer/path/allpaths.c
@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *       $PostgreSQL: pgsql/src/backend/optimizer/path/allpaths.c,v 1.163 2007/04/21 21:01:44 tgl Exp $
+ *       $PostgreSQL: pgsql/src/backend/optimizer/path/allpaths.c,v 1.164 2007/05/26 18:23:01 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -45,6 +45,7 @@ static void set_plain_rel_pathlist(PlannerInfo *root, RelOptInfo *rel,
                                           RangeTblEntry *rte);
 static void set_append_rel_pathlist(PlannerInfo *root, RelOptInfo *rel,
                                                Index rti, RangeTblEntry *rte);
+static void set_dummy_rel_pathlist(RelOptInfo *rel);
 static void set_subquery_pathlist(PlannerInfo *root, RelOptInfo *rel,
                                          Index rti, RangeTblEntry *rte);
 static void set_function_pathlist(PlannerInfo *root, RelOptInfo *rel,
@@ -198,23 +199,14 @@ set_plain_rel_pathlist(PlannerInfo *root, RelOptInfo *rel, RangeTblEntry *rte)
 {
        /*
         * If we can prove we don't need to scan the rel via constraint exclusion,
-        * set up a single dummy path for it.  (Rather than inventing a special
-        * "dummy" path type, we represent this as an AppendPath with no members.)
-        * We only need to check for regular baserels; if it's an otherrel, CE
-        * was already checked in set_append_rel_pathlist().
+        * set up a single dummy path for it.  We only need to check for regular
+        * baserels; if it's an otherrel, CE was already checked in
+        * set_append_rel_pathlist().
         */
        if (rel->reloptkind == RELOPT_BASEREL &&
                relation_excluded_by_constraints(rel, rte))
        {
-               /* Set dummy size estimates --- we leave attr_widths[] as zeroes */
-               rel->rows = 0;
-               rel->width = 0;
-
-               add_path(rel, (Path *) create_append_path(rel, NIL));
-
-               /* Select cheapest path (pretty easy in this case...) */
-               set_cheapest(rel);
-
+               set_dummy_rel_pathlist(rel);
                return;
        }
 
@@ -330,7 +322,12 @@ set_append_rel_pathlist(PlannerInfo *root, RelOptInfo *rel,
 
                if (relation_excluded_by_constraints(childrel, childRTE))
                {
-                       /* this child need not be scanned, so just disregard it */
+                       /*
+                        * This child need not be scanned, so we can omit it from the
+                        * appendrel.  Mark it with a dummy cheapest-path though, in
+                        * case best_appendrel_indexscan() looks at it later.
+                        */
+                       set_dummy_rel_pathlist(childrel);
                        continue;
                }
 
@@ -425,6 +422,26 @@ set_append_rel_pathlist(PlannerInfo *root, RelOptInfo *rel,
        set_cheapest(rel);
 }
 
+/*
+ * set_dummy_rel_pathlist
+ *       Build a dummy path for a relation that's been excluded by constraints
+ *
+ * Rather than inventing a special "dummy" path type, we represent this as an
+ * AppendPath with no members.
+ */
+static void
+set_dummy_rel_pathlist(RelOptInfo *rel)
+{
+       /* Set dummy size estimates --- we leave attr_widths[] as zeroes */
+       rel->rows = 0;
+       rel->width = 0;
+
+       add_path(rel, (Path *) create_append_path(rel, NIL));
+
+       /* Select cheapest path (pretty easy in this case...) */
+       set_cheapest(rel);
+}
+
 /* quick-and-dirty test to see if any joining is needed */
 static bool
 has_multiple_baserels(PlannerInfo *root)