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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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17
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 1.146 2003/02/09 23:57:19 tgl Exp $
* $Header: /cvsroot/pgsql/src/backend/optimizer/plan/planner.c,v 1.147 2003/02/15 20:12:40 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@ -469,6 +469,9 @@ inheritance_planner(Query *parse, List *inheritlist)
/* Save the target-relations list for the executor, too */
parse->resultRelations = inheritlist;
/* Mark result as unordered (probably unnecessary) */
parse->query_pathkeys = NIL;
return (Plan *) make_append(subplans, true, tlist);
}
@ -491,7 +494,8 @@ inheritance_planner(Query *parse, List *inheritlist)
* The normal case is to pass -1, but some callers pass values >= 0 to
* override this routine's determination of the appropriate fraction.
*
* Returns a query plan.
* Returns a query plan. Also, parse->query_pathkeys is returned as the
* actual output ordering of the plan (in pathkey format).
*--------------------
*/
static Plan *
@ -1191,10 +1195,13 @@ grouping_planner(Query *parse, double tuple_fraction)
if (parse->sortClause)
{
if (!pathkeys_contained_in(sort_pathkeys, current_pathkeys))
{
result_plan = (Plan *) make_sort_from_sortclauses(parse,
tlist,
result_plan,
parse->sortClause);
current_pathkeys = sort_pathkeys;
}
}
/*
@ -1232,6 +1239,12 @@ grouping_planner(Query *parse, double tuple_fraction)
parse->limitCount);
}
/*
* Return the actual output ordering in query_pathkeys for possible
* use by an outer query level.
*/
parse->query_pathkeys = current_pathkeys;
return result_plan;
}