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Create a third option named "partition" for constraint_exclusion, and make it

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the default.  This setting enables constraint exclusion checks only for
appendrel members (ie, inheritance children and UNION ALL arms), which are
the cases in which constraint exclusion is most likely to be useful.  Avoiding
the overhead for simple queries that are unlikely to benefit should bring
the cost down to the point where this is a reasonable default setting.
Per today's discussion.
This commit is contained in:
Tom Lane
2009-01-07 22:40:49 +00:00
parent 12dcf7bb75
commit 445ce15702
7 changed files with 92 additions and 45 deletions
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16
src/backend/optimizer/util/plancat.c
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@@ -9,7 +9,7 @@
*
*
* IDENTIFICATION
* $PostgreSQL: pgsql/src/backend/optimizer/util/plancat.c,v 1.153 2009/01/01 17:23:45 momjian Exp $
* $PostgreSQL: pgsql/src/backend/optimizer/util/plancat.c,v 1.154 2009/01/07 22:40:49 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@@ -27,6 +27,7 @@
#include "nodes/makefuncs.h"
#include "nodes/nodeFuncs.h"
#include "optimizer/clauses.h"
#include "optimizer/cost.h"
#include "optimizer/plancat.h"
#include "optimizer/predtest.h"
#include "optimizer/prep.h"
@@ -43,7 +44,7 @@
/* GUC parameter */
bool constraint_exclusion = false;
int constraint_exclusion = CONSTRAINT_EXCLUSION_PARTITION;
/* Hook for plugins to get control in get_relation_info() */
get_relation_info_hook_type get_relation_info_hook = NULL;
@@ -561,8 +562,9 @@ get_relation_constraints(PlannerInfo *root,
* self-inconsistent restrictions, or restrictions inconsistent with the
* relation's CHECK constraints.
*
* Note: this examines only rel->relid and rel->baserestrictinfo; therefore
* it can be called before filling in other fields of the RelOptInfo.
* Note: this examines only rel->relid, rel->reloptkind, and
* rel->baserestrictinfo; therefore it can be called before filling in
* other fields of the RelOptInfo.
*/
bool
relation_excluded_by_constraints(PlannerInfo *root,
@@ -573,8 +575,10 @@ relation_excluded_by_constraints(PlannerInfo *root,
List *safe_constraints;
ListCell *lc;
/* Skip the test if constraint exclusion is disabled */
if (!constraint_exclusion)
/* Skip the test if constraint exclusion is disabled for the rel */
if (constraint_exclusion == CONSTRAINT_EXCLUSION_OFF ||
(constraint_exclusion == CONSTRAINT_EXCLUSION_PARTITION &&
rel->reloptkind != RELOPT_OTHER_MEMBER_REL))
return false;
/*