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Planner speedup hacking. Avoid saving useless pathkeys, so that path

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comparison does not consider paths different when they differ only in
uninteresting aspects of sort order.  (We had a special case of this
consideration for indexscans already, but generalize it to apply to
ordered join paths too.)  Be stricter about what is a canonical pathkey
to allow faster pathkey comparison.  Cache canonical pathkeys and
dispersion stats for left and right sides of a RestrictInfo's clause,
to avoid repeated computation.  Total speedup will depend on number of
tables in a query, but I see about 4x speedup of planning phase for
a sample seven-table query.
This commit is contained in:
Tom Lane
2000-12-14 22:30:45 +00:00
parent db11f4382a
commit ea166f1146
16 changed files with 622 additions and 365 deletions
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11
src/backend/optimizer/plan/planner.c
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@ -8,7 +8,7 @@
*
*
* IDENTIFICATION
* $Header: /cvsroot/pgsql/src/backend/optimizer/plan/planner.c,v 1.97 2000/12/06 23:55:17 tgl Exp $
* $Header: /cvsroot/pgsql/src/backend/optimizer/plan/planner.c,v 1.98 2000/12/14 22:30:43 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@ -931,13 +931,12 @@ grouping_planner(Query *parse, double tuple_fraction)
* If both GROUP BY and ORDER BY are specified, we will need
* two levels of sort --- and, therefore, certainly need to
* read all the input tuples --- unless ORDER BY is a subset
* of GROUP BY. (Although we are comparing non-canonicalized
* pathkeys here, it should be OK since they will both contain
* only single-element sublists at this point. See
* pathkeys.c.)
* of GROUP BY. (We have not yet canonicalized the pathkeys,
* so must use the slower noncanonical comparison method.)
*/
if (parse->groupClause && parse->sortClause &&
!pathkeys_contained_in(sort_pathkeys, group_pathkeys))
!noncanonical_pathkeys_contained_in(sort_pathkeys,
group_pathkeys))
tuple_fraction = 0.0;
}
else if (parse->hasAggs)