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Avoid running build_index_pathkeys() in situations where there cannot

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possibly be any useful pathkeys --- to wit, queries with neither any
join clauses nor any ORDER BY request.  It's nearly free to check for
this case and it saves a useful fraction of the planning time for simple
queries.
This commit is contained in:
Tom Lane
2007-04-15 20:09:28 +00:00
parent f97d4a267a
commit fa92d21a48
3 changed files with 37 additions and 6 deletions
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9
src/backend/optimizer/path/indxpath.c
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@ -9,7 +9,7 @@
*
*
* IDENTIFICATION
* $PostgreSQL: pgsql/src/backend/optimizer/path/indxpath.c,v 1.219 2007/04/06 22:33:42 tgl Exp $
* $PostgreSQL: pgsql/src/backend/optimizer/path/indxpath.c,v 1.220 2007/04/15 20:09:28 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@ -251,6 +251,7 @@ find_usable_indexes(PlannerInfo *root, RelOptInfo *rel,
SaOpControl saop_control)
{
Relids outer_relids = outer_rel ? outer_rel->relids : NULL;
bool possibly_useful_pathkeys = has_useful_pathkeys(root, rel);
List *result = NIL;
List *all_clauses = NIL; /* not computed till needed */
ListCell *ilist;
@ -337,7 +338,8 @@ find_usable_indexes(PlannerInfo *root, RelOptInfo *rel,
* relevant unless we are at top level.
*/
index_is_ordered = OidIsValid(index->fwdsortop[0]);
if (index_is_ordered && istoplevel && outer_rel == NULL)
if (index_is_ordered && possibly_useful_pathkeys &&
istoplevel && outer_rel == NULL)
{
index_pathkeys = build_index_pathkeys(root, index,
ForwardScanDirection);
@ -369,7 +371,8 @@ find_usable_indexes(PlannerInfo *root, RelOptInfo *rel,
* 4. If the index is ordered, a backwards scan might be
* interesting. Again, this is only interesting at top level.
*/
if (index_is_ordered && istoplevel && outer_rel == NULL)
if (index_is_ordered && possibly_useful_pathkeys &&
istoplevel && outer_rel == NULL)
{
index_pathkeys = build_index_pathkeys(root, index,
BackwardScanDirection);