diff options
Diffstat (limited to 'src/backend/optimizer/plan/planner.c')
| -rw-r--r-- | src/backend/optimizer/plan/planner.c | 30 |
1 files changed, 21 insertions, 9 deletions
diff --git a/src/backend/optimizer/plan/planner.c b/src/backend/optimizer/plan/planner.c index d5dc6f7c7e6..366c50f2730 100644 --- a/src/backend/optimizer/plan/planner.c +++ b/src/backend/optimizer/plan/planner.c @@ -8,7 +8,7 @@ * * * IDENTIFICATION - * $PostgreSQL: pgsql/src/backend/optimizer/plan/planner.c,v 1.218 2007/04/27 22:05:47 tgl Exp $ + * $PostgreSQL: pgsql/src/backend/optimizer/plan/planner.c,v 1.219 2007/05/04 01:13:44 tgl Exp $ * *------------------------------------------------------------------------- */ @@ -61,7 +61,8 @@ static double preprocess_limit(PlannerInfo *root, double tuple_fraction, int64 *offset_est, int64 *count_est); static Oid *extract_grouping_ops(List *groupClause); -static bool choose_hashed_grouping(PlannerInfo *root, double tuple_fraction, +static bool choose_hashed_grouping(PlannerInfo *root, + double tuple_fraction, double limit_tuples, Path *cheapest_path, Path *sorted_path, Oid *groupOperators, double dNumGroups, AggClauseCounts *agg_counts); @@ -696,6 +697,7 @@ grouping_planner(PlannerInfo *root, double tuple_fraction) List *tlist = parse->targetList; int64 offset_est = 0; int64 count_est = 0; + double limit_tuples = -1.0; Plan *result_plan; List *current_pathkeys; List *sort_pathkeys; @@ -703,8 +705,16 @@ grouping_planner(PlannerInfo *root, double tuple_fraction) /* Tweak caller-supplied tuple_fraction if have LIMIT/OFFSET */ if (parse->limitCount || parse->limitOffset) + { tuple_fraction = preprocess_limit(root, tuple_fraction, &offset_est, &count_est); + /* + * If we have a known LIMIT, and don't have an unknown OFFSET, + * we can estimate the effects of using a bounded sort. + */ + if (count_est > 0 && offset_est >= 0) + limit_tuples = (double) count_est + (double) offset_est; + } if (parse->setOperations) { @@ -850,7 +860,7 @@ grouping_planner(PlannerInfo *root, double tuple_fraction) * estimate the number of groups in the query, and canonicalize all * the pathkeys. */ - query_planner(root, sub_tlist, tuple_fraction, + query_planner(root, sub_tlist, tuple_fraction, limit_tuples, &cheapest_path, &sorted_path, &dNumGroups); group_pathkeys = root->group_pathkeys; @@ -864,7 +874,7 @@ grouping_planner(PlannerInfo *root, double tuple_fraction) { groupOperators = extract_grouping_ops(parse->groupClause); use_hashed_grouping = - choose_hashed_grouping(root, tuple_fraction, + choose_hashed_grouping(root, tuple_fraction, limit_tuples, cheapest_path, sorted_path, groupOperators, dNumGroups, &agg_counts); @@ -1099,7 +1109,8 @@ grouping_planner(PlannerInfo *root, double tuple_fraction) { result_plan = (Plan *) make_sort_from_pathkeys(root, result_plan, - sort_pathkeys); + sort_pathkeys, + limit_tuples); current_pathkeys = sort_pathkeys; } } @@ -1414,7 +1425,8 @@ extract_grouping_ops(List *groupClause) * choose_hashed_grouping - should we use hashed grouping? */ static bool -choose_hashed_grouping(PlannerInfo *root, double tuple_fraction, +choose_hashed_grouping(PlannerInfo *root, + double tuple_fraction, double limit_tuples, Path *cheapest_path, Path *sorted_path, Oid *groupOperators, double dNumGroups, AggClauseCounts *agg_counts) @@ -1499,7 +1511,7 @@ choose_hashed_grouping(PlannerInfo *root, double tuple_fraction, /* Result of hashed agg is always unsorted */ if (root->sort_pathkeys) cost_sort(&hashed_p, root, root->sort_pathkeys, hashed_p.total_cost, - dNumGroups, cheapest_path_width); + dNumGroups, cheapest_path_width, limit_tuples); if (sorted_path) { @@ -1516,7 +1528,7 @@ choose_hashed_grouping(PlannerInfo *root, double tuple_fraction, if (!pathkeys_contained_in(root->group_pathkeys, current_pathkeys)) { cost_sort(&sorted_p, root, root->group_pathkeys, sorted_p.total_cost, - cheapest_path_rows, cheapest_path_width); + cheapest_path_rows, cheapest_path_width, -1.0); current_pathkeys = root->group_pathkeys; } @@ -1533,7 +1545,7 @@ choose_hashed_grouping(PlannerInfo *root, double tuple_fraction, if (root->sort_pathkeys && !pathkeys_contained_in(root->sort_pathkeys, current_pathkeys)) cost_sort(&sorted_p, root, root->sort_pathkeys, sorted_p.total_cost, - dNumGroups, cheapest_path_width); + dNumGroups, cheapest_path_width, limit_tuples); /* * Now make the decision using the top-level tuple fraction. First we |