*
*
* IDENTIFICATION
- * $PostgreSQL: pgsql/src/backend/optimizer/plan/planner.c,v 1.206 2006/08/02 01:59:46 joe Exp $
+ * $PostgreSQL: pgsql/src/backend/optimizer/plan/planner.c,v 1.207 2006/08/05 17:21:52 tgl Exp $
*
*-------------------------------------------------------------------------
*/
static void preprocess_qual_conditions(PlannerInfo *root, Node *jtnode);
static Plan *inheritance_planner(PlannerInfo *root);
static Plan *grouping_planner(PlannerInfo *root, double tuple_fraction);
+static bool is_dummy_plan(Plan *plan);
static double preprocess_limit(PlannerInfo *root,
double tuple_fraction,
int64 *offset_est, int64 *count_est);
Query *parse = root->parse;
int parentRTindex = parse->resultRelation;
List *subplans = NIL;
+ List *rtable = NIL;
List *tlist = NIL;
PlannerInfo subroot;
ListCell *l;
- subroot.parse = NULL; /* catch it if no matches in loop */
-
parse->resultRelations = NIL;
foreach(l, root->append_rel_list)
if (appinfo->parent_relid != parentRTindex)
continue;
- /* Build target-relations list for the executor */
- parse->resultRelations = lappend_int(parse->resultRelations,
- appinfo->child_relid);
-
/*
* Generate modified query with this rel as target. We have to be
* prepared to translate varnos in in_info_list as well as in the
/* Generate plan */
subplan = grouping_planner(&subroot, 0.0 /* retrieve all tuples */ );
- subplans = lappend(subplans, subplan);
+ /*
+ * If this child rel was excluded by constraint exclusion, exclude
+ * it from the plan.
+ */
+ if (is_dummy_plan(subplan))
+ continue;
- /* Save preprocessed tlist from first rel for use in Append */
- if (tlist == NIL)
+ /* Save rtable and tlist from first rel for use below */
+ if (subplans == NIL)
+ {
+ rtable = subroot.parse->rtable;
tlist = subplan->targetlist;
+ }
+
+ subplans = lappend(subplans, subplan);
+
+ /* Build target-relations list for the executor */
+ parse->resultRelations = lappend_int(parse->resultRelations,
+ appinfo->child_relid);
}
+ /* Mark result as unordered (probably unnecessary) */
+ root->query_pathkeys = NIL;
+
+ /*
+ * If we managed to exclude every child rel, return a dummy plan
+ */
+ if (subplans == NIL)
+ return (Plan *) make_result(tlist,
+ (Node *) list_make1(makeBoolConst(false,
+ false)),
+ NULL);
+
/*
* Planning might have modified the rangetable, due to changes of the
* Query structures inside subquery RTEs. We have to ensure that this
*
* XXX should clean this up someday
*/
- parse->rtable = subroot.parse->rtable;
-
- /* Mark result as unordered (probably unnecessary) */
- root->query_pathkeys = NIL;
+ parse->rtable = rtable;
return (Plan *) make_append(subplans, true, tlist);
}
}
/*
+ * Detect whether a plan node is a "dummy" plan created when a relation
+ * is deemed not to need scanning due to constraint exclusion.
+ *
+ * Currently, such dummy plans are Result nodes with constant FALSE
+ * filter quals.
+ */
+static bool
+is_dummy_plan(Plan *plan)
+{
+ if (IsA(plan, Result))
+ {
+ List *rcqual = (List *) ((Result *) plan)->resconstantqual;
+
+ if (list_length(rcqual) == 1)
+ {
+ Const *constqual = (Const *) linitial(rcqual);
+
+ if (constqual && IsA(constqual, Const))
+ {
+ if (!constqual->constisnull &&
+ !DatumGetBool(constqual->constvalue))
+ return true;
+ }
+ }
+ }
+ return false;
+}
+
+/*
* preprocess_limit - do pre-estimation for LIMIT and/or OFFSET clauses
*
* We try to estimate the values of the LIMIT/OFFSET clauses, and pass the