From eeec8b83542a722876231ceb14e4f2fffb1fc001 Mon Sep 17 00:00:00 2001 From: Richard Guo Date: Mon, 9 Sep 2024 19:57:53 +0900 Subject: [PATCH v1] Consider explicit incremental sort for mergejoins --- src/backend/optimizer/path/costsize.c | 60 +++++++++++++++---- src/backend/optimizer/plan/createplan.c | 80 ++++++++++++++++++++++--- 2 files changed, 120 insertions(+), 20 deletions(-) diff --git a/src/backend/optimizer/path/costsize.c b/src/backend/optimizer/path/costsize.c index e1523d15df..210fe5e754 100644 --- a/src/backend/optimizer/path/costsize.c +++ b/src/backend/optimizer/path/costsize.c @@ -3532,7 +3532,8 @@ final_cost_nestloop(PlannerInfo *root, NestPath *path, * join quals here, except for obtaining the scan selectivity estimate which * is really essential (but fortunately, use of caching keeps the cost of * getting that down to something reasonable). - * We also assume that cost_sort is cheap enough to use here. + * We also assume that cost_sort/cost_incremental_sort is cheap enough to use + * here. * * 'workspace' is to be filled with startup_cost, total_cost, and perhaps * other data to be used by final_cost_mergejoin @@ -3569,7 +3570,8 @@ initial_cost_mergejoin(PlannerInfo *root, JoinCostWorkspace *workspace, outerendsel, innerstartsel, innerendsel; - Path sort_path; /* dummy for result of cost_sort */ + Path sort_path; /* dummy for result of + * cost_sort/cost_incremental_sort */ /* Protect some assumptions below that rowcounts aren't zero */ if (outer_path_rows <= 0) @@ -3682,16 +3684,50 @@ initial_cost_mergejoin(PlannerInfo *root, JoinCostWorkspace *workspace, if (outersortkeys) /* do we need to sort outer? */ { - cost_sort(&sort_path, - root, - outersortkeys, - outer_path->disabled_nodes, - outer_path->total_cost, - outer_path_rows, - outer_path->pathtarget->width, - 0.0, - work_mem, - -1.0); + bool use_incremental_sort = false; + int presorted_keys; + + if (enable_incremental_sort) + { + bool is_sorted PG_USED_FOR_ASSERTS_ONLY; + + is_sorted = pathkeys_count_contained_in(outersortkeys, + outer_path->pathkeys, + &presorted_keys); + Assert(!is_sorted); + + if (presorted_keys > 0) + use_incremental_sort = true; + } + + if (!use_incremental_sort) + { + cost_sort(&sort_path, + root, + outersortkeys, + outer_path->disabled_nodes, + outer_path->total_cost, + outer_path_rows, + outer_path->pathtarget->width, + 0.0, + work_mem, + -1.0); + } + else + { + cost_incremental_sort(&sort_path, + root, + outersortkeys, + presorted_keys, + outer_path->disabled_nodes, + outer_path->startup_cost, + outer_path->total_cost, + outer_path_rows, + outer_path->pathtarget->width, + 0.0, + work_mem, + -1.0); + } disabled_nodes += sort_path.disabled_nodes; startup_cost += sort_path.startup_cost; startup_cost += (sort_path.total_cost - sort_path.startup_cost) diff --git a/src/backend/optimizer/plan/createplan.c b/src/backend/optimizer/plan/createplan.c index bb45ef318f..bff48d266f 100644 --- a/src/backend/optimizer/plan/createplan.c +++ b/src/backend/optimizer/plan/createplan.c @@ -179,6 +179,8 @@ static void copy_generic_path_info(Plan *dest, Path *src); static void copy_plan_costsize(Plan *dest, Plan *src); static void label_sort_with_costsize(PlannerInfo *root, Sort *plan, double limit_tuples); +static void label_incrementalsort_with_costsize(PlannerInfo *root, IncrementalSort *plan, + List *pathkeys, double limit_tuples); static SeqScan *make_seqscan(List *qptlist, List *qpqual, Index scanrelid); static SampleScan *make_samplescan(List *qptlist, List *qpqual, Index scanrelid, TableSampleClause *tsc); @@ -4523,12 +4525,47 @@ create_mergejoin_plan(PlannerInfo *root, if (best_path->outersortkeys) { Relids outer_relids = outer_path->parent->relids; - Sort *sort = make_sort_from_pathkeys(outer_plan, + Plan *sort_plan; + bool use_incremental_sort = false; + int presorted_keys; + + if (enable_incremental_sort) + { + bool is_sorted PG_USED_FOR_ASSERTS_ONLY; + + is_sorted = pathkeys_count_contained_in(best_path->outersortkeys, + outer_path->pathkeys, + &presorted_keys); + Assert(!is_sorted); + + if (presorted_keys > 0) + use_incremental_sort = true; + } + + if (!use_incremental_sort) + { + sort_plan = (Plan *) + make_sort_from_pathkeys(outer_plan, + best_path->outersortkeys, + outer_relids); + + label_sort_with_costsize(root, (Sort *) sort_plan, -1.0); + } + else + { + sort_plan = (Plan *) + make_incrementalsort_from_pathkeys(outer_plan, best_path->outersortkeys, - outer_relids); + outer_relids, + presorted_keys); - label_sort_with_costsize(root, sort, -1.0); - outer_plan = (Plan *) sort; + label_incrementalsort_with_costsize(root, + (IncrementalSort *) sort_plan, + best_path->outersortkeys, + -1.0); + } + + outer_plan = sort_plan; outerpathkeys = best_path->outersortkeys; } else @@ -5447,10 +5484,6 @@ label_sort_with_costsize(PlannerInfo *root, Sort *plan, double limit_tuples) Plan *lefttree = plan->plan.lefttree; Path sort_path; /* dummy for result of cost_sort */ - /* - * This function shouldn't have to deal with IncrementalSort plans because - * they are only created from corresponding Path nodes. - */ Assert(IsA(plan, Sort)); cost_sort(&sort_path, root, NIL, @@ -5469,6 +5502,37 @@ label_sort_with_costsize(PlannerInfo *root, Sort *plan, double limit_tuples) plan->plan.parallel_safe = lefttree->parallel_safe; } +/* + * Same as label_sort_with_costsize, but labels the IncrementalSort node + * instead. + */ +static void +label_incrementalsort_with_costsize(PlannerInfo *root, IncrementalSort *plan, + List *pathkeys, double limit_tuples) +{ + Plan *lefttree = plan->sort.plan.lefttree; + Path sort_path; /* dummy for result of cost_incremental_sort */ + + Assert(IsA(plan, IncrementalSort)); + + cost_incremental_sort(&sort_path, root, pathkeys, + plan->nPresortedCols, + plan->sort.plan.disabled_nodes, + lefttree->startup_cost, + lefttree->total_cost, + lefttree->plan_rows, + lefttree->plan_width, + 0.0, + work_mem, + limit_tuples); + plan->sort.plan.startup_cost = sort_path.startup_cost; + plan->sort.plan.total_cost = sort_path.total_cost; + plan->sort.plan.plan_rows = lefttree->plan_rows; + plan->sort.plan.plan_width = lefttree->plan_width; + plan->sort.plan.parallel_aware = false; + plan->sort.plan.parallel_safe = lefttree->parallel_safe; +} + /* * bitmap_subplan_mark_shared * Set isshared flag in bitmap subplan so that it will be created in -- 2.43.0