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Fix inheritance_planner() to delete dummy subplans from its Append plan

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list, when some of the child rels have been excluded by constraint
exclusion.  This doesn't save a huge amount of time but it'll save some,
and it makes the EXPLAIN output look saner.  We already did the
equivalent thing in set_append_rel_pathlist(), but not here.
This commit is contained in:
Tom Lane 2006-08-05 17:21:52 +00:00
parent 1d28bf2589
commit 635d42e9c3
1 changed files with 62 additions and 14 deletions
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76
src/backend/optimizer/plan/planner.c
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@ -8,7 +8,7 @@
*
*
* 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 $
*
*-------------------------------------------------------------------------
*/
@ -58,6 +58,7 @@ static Node *preprocess_expression(PlannerInfo *root, Node *expr, int kind);
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);
@ -553,12 +554,11 @@ inheritance_planner(PlannerInfo *root)
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)
@ -570,10 +570,6 @@ inheritance_planner(PlannerInfo *root)
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
@ -592,13 +588,39 @@ inheritance_planner(PlannerInfo *root)
/* Generate plan */
subplan = grouping_planner(&subroot, 0.0 /* retrieve all tuples */ );
/*
* If this child rel was excluded by constraint exclusion, exclude
* it from the plan.
*/
if (is_dummy_plan(subplan))
continue;
/* Save rtable and tlist from first rel for use below */
if (subplans == NIL)
{
rtable = subroot.parse->rtable;
tlist = subplan->targetlist;
}
subplans = lappend(subplans, subplan);
/* Save preprocessed tlist from first rel for use in Append */
if (tlist == NIL)
tlist = subplan->targetlist;
/* 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
@ -610,10 +632,7 @@ inheritance_planner(PlannerInfo *root)
*
* 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);
}
@ -1072,6 +1091,35 @@ grouping_planner(PlannerInfo *root, double tuple_fraction)
return result_plan;
}
/*
* 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
*