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Teach planner how to propagate pathkeys from sub-SELECTs in FROM up to

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the outer query.  (The implementation is a bit klugy, but it would take
nontrivial restructuring to make it nicer, which this is probably not
worth.)  This avoids unnecessary sort steps in examples like
SELECT foo,count(*) FROM (SELECT ... ORDER BY foo,bar) sub GROUP BY foo
which means there is now a reasonable technique for controlling the
order of inputs to custom aggregates, even in the grouping case.
This commit is contained in:
Tom Lane
2003-02-15 20:12:41 +00:00
parent 50c4190e37
commit 056467ec6b
9 changed files with 172 additions and 29 deletions
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4
src/include/optimizer/paths.h
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@@ -8,7 +8,7 @@
* Portions Copyright (c) 1996-2002, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
*
* $Id: paths.h,v 1.65 2003/01/25 23:10:30 tgl Exp $
* $Id: paths.h,v 1.66 2003/02/15 20:12:41 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@@ -104,6 +104,8 @@ extern Path *get_cheapest_fractional_path_for_pathkeys(List *paths,
extern List *build_index_pathkeys(Query *root, RelOptInfo *rel,
IndexOptInfo *index,
ScanDirection scandir);
extern List *build_subquery_pathkeys(Query *root, RelOptInfo *rel,
Query *subquery);
extern List *build_join_pathkeys(Query *root,
RelOptInfo *joinrel,
List *outer_pathkeys);