mirrors/postgres
1
0
Fork 0
Code Issues Pull Requests Packages Projects Releases Wiki Activity

Save a few cycles in simple cases: no need to call cost_sort() when there

Browse Source 
is no presorted path to compare with.
This commit is contained in:
Tom Lane 2000-03-24 21:40:43 +00:00
parent c07118b3b3
commit 8cbeb5f131
1 changed files with 8 additions and 8 deletions

16
src/backend/optimizer/plan/planmain.c

@ -14,7 +14,7 @@
*
*
* IDENTIFICATION
* $Header: /cvsroot/pgsql/src/backend/optimizer/plan/planmain.c,v 1.53 2000/03/21 05:11:58 tgl Exp $
* $Header: /cvsroot/pgsql/src/backend/optimizer/plan/planmain.c,v 1.54 2000/03/24 21:40:43 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@ -174,7 +174,6 @@ subplanner(Query *root,
{
RelOptInfo *final_rel;
Path *cheapestpath;
Path sort_path; /* dummy for result of cost_sort */
Path *presortedpath;
/*
@ -288,21 +287,22 @@ subplanner(Query *root,
* cheaper than doing an explicit sort on the cheapest-total-cost path.
*/
cheapestpath = final_rel->cheapest_total_path;
cost_sort(&sort_path, root->query_pathkeys,
final_rel->rows, final_rel->width);
sort_path.startup_cost += cheapestpath->total_cost;
sort_path.total_cost += cheapestpath->total_cost;
presortedpath =
get_cheapest_fractional_path_for_pathkeys(final_rel->pathlist,
root->query_pathkeys,
tuple_fraction);
if (presortedpath)
{
Path sort_path; /* dummy for result of cost_sort */
cost_sort(&sort_path, root->query_pathkeys,
final_rel->rows, final_rel->width);
sort_path.startup_cost += cheapestpath->total_cost;
sort_path.total_cost += cheapestpath->total_cost;
if (compare_fractional_path_costs(presortedpath, &sort_path,
tuple_fraction) <= 0)
{
/* Found a better presorted path, use it */
/* Presorted path is cheaper, use it */
root->query_pathkeys = presortedpath->pathkeys;
return create_plan(root, presortedpath);
}