Avoid assuming that statistics for a parent relation reflect the properties of

the union of its child relations as well.  This might have been a good idea
when it was originally coded, but it's a fatally bad idea when inheritance is
being used for partitioning.  It's better to have no stats at all than
completely misleading stats.  Per report from Mark Liberman.

The bug arguably exists all the way back, but I've only patched HEAD and 8.1
because we weren't particularly trying to support partitioning before 8.1.

Eventually we ought to look at deriving union statistics instead of just
punting, but for now the drop kick looks good.

diff --git a/src/backend/optimizer/path/allpaths.c b/src/backend/optimizer/path/allpaths.c
index f35e87962dac21f7eafa04f64e27a2b5680538f7..de82c3df8d08308e67e889b253bdcd9af7e6ca23 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 1.145 2006/04/30 18:30:39 tgl Exp $
+ *       $PostgreSQL: pgsql/src/backend/optimizer/path/allpaths.c,v 1.146 2006/05/02 04:34:18 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -273,6 +273,13 @@ set_append_rel_pathlist(PlannerInfo *root, RelOptInfo *rel,
                                (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
                                 errmsg("SELECT FOR UPDATE/SHARE is not supported for inheritance queries")));
 
+       /*
+        * We might have looked up indexes for the parent rel, but they're
+        * really not relevant to the appendrel.  Reset the pointer to avoid
+        * any confusion.
+        */
+       rel->indexlist = NIL;
+
        /*
         * Initialize to compute size estimates for whole append relation
         */

diff --git a/src/backend/utils/adt/selfuncs.c b/src/backend/utils/adt/selfuncs.c
index 082089b9f112cefcad169524a6a601554876ec24..5f830ef0cd3a8422ac0b5acb77c1a28b22ee75a7 100644 (file)
--- a/src/backend/utils/adt/selfuncs.c
+++ b/src/backend/utils/adt/selfuncs.c
@@ -15,7 +15,7 @@
  *
  *
  * IDENTIFICATION
- *       $PostgreSQL: pgsql/src/backend/utils/adt/selfuncs.c,v 1.203 2006/04/27 17:52:40 tgl Exp $
+ *       $PostgreSQL: pgsql/src/backend/utils/adt/selfuncs.c,v 1.204 2006/05/02 04:34:18 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -3265,19 +3265,27 @@ examine_variable(PlannerInfo *root, Node *node, int varRelid,
                (varRelid == 0 || varRelid == ((Var *) basenode)->varno))
        {
                Var                *var = (Var *) basenode;
-               Oid                     relid;
+               RangeTblEntry *rte;
 
                vardata->var = basenode;        /* return Var without relabeling */
                vardata->rel = find_base_rel(root, var->varno);
                vardata->atttype = var->vartype;
                vardata->atttypmod = var->vartypmod;
 
-               relid = getrelid(var->varno, root->parse->rtable);
+               rte = rt_fetch(var->varno, root->parse->rtable);
 
-               if (OidIsValid(relid))
+               if (rte->inh)
+               {
+                       /*
+                        * XXX This means the Var represents a column of an append relation.
+                        * Later add code to look at the member relations and try to derive
+                        * some kind of combined statistics?
+                        */
+               }
+               else if (rte->rtekind == RTE_RELATION)
                {
                        vardata->statsTuple = SearchSysCache(STATRELATT,
-                                                                                                ObjectIdGetDatum(relid),
+                                                                                                ObjectIdGetDatum(rte->relid),
                                                                                                 Int16GetDatum(var->varattno),
                                                                                                 0, 0);
                }