From 159936c405e51b721e14033af35d886f9948b959 Mon Sep 17 00:00:00 2001 From: Alexander Korotkov Date: Thu, 11 Jan 2024 13:26:49 +0200 Subject: [PATCH 2/2] Explore alternative orderings of group-by pathkeys during optimization. When evaluating a query with a multi-column GROUP BY clause, we can minimize sort operations or avoid them if we synchronize the order of GROUP BY clauses with the ORDER BY sort clause or sort order, which comes from the underlying query tree. Grouping does not imply any ordering, so we can compare the keys in arbitrary order, and a Hash Agg leverages this. But for Group Agg, we simply compared keys in the order specified in the query. This commit explores alternative ordering of the keys, trying to find a cheaper one. The ordering of group keys may interact with other parts of the query, some of which may not be known while planning the grouping. For example, there may be an explicit ORDER BY clause or some other ordering-dependent operation higher up in the query, and using the same ordering may allow using either incremental sort or even eliminating the sort entirely. The patch always keeps the ordering specified in the query, assuming the user might have additional insights. This introduces a new GUC enable_group_by_reordering so that the optimization may be disabled if needed. Discussion: https://postgr.es/m/7c79e6a5-8597-74e8-0671-1c39d124c9d6%40sigaev.ru Author: Andrey V. Lepikhov, Teodor Sigaev Reviewed-by: Tomas Vondra, Claudio Freire, Gavin Flower, Dmitry Dolgov Reviewed-by: Robert Haas, Pavel Borisov, David Rowley, Zhihong Yu Reviewed-by: Tom Lane, Alexander Korotkov --- src/backend/optimizer/path/equivclass.c | 13 +- src/backend/optimizer/path/pathkeys.c | 220 ++++++++++++ src/backend/optimizer/plan/planner.c | 316 +++++++++++------- src/backend/utils/misc/guc_tables.c | 10 + src/backend/utils/misc/postgresql.conf.sample | 1 + src/include/nodes/pathnodes.h | 10 + src/include/optimizer/paths.h | 2 + src/test/regress/expected/aggregates.out | 154 +++++++++ src/test/regress/expected/sysviews.out | 3 +- src/test/regress/sql/aggregates.sql | 56 ++++ src/tools/pgindent/typedefs.list | 1 + 11 files changed, 661 insertions(+), 125 deletions(-) diff --git a/src/backend/optimizer/path/equivclass.c b/src/backend/optimizer/path/equivclass.c index e86dfeaecd4..7dd14d0a43b 100644 --- a/src/backend/optimizer/path/equivclass.c +++ b/src/backend/optimizer/path/equivclass.c @@ -652,7 +652,18 @@ get_eclass_for_sort_expr(PlannerInfo *root, if (opcintype == cur_em->em_datatype && equal(expr, cur_em->em_expr)) - return cur_ec; /* Match! */ + { + /* + * Match! + * + * Copy the sortref if it wasn't set yet. That may happen if + * the ec was constructed from WHERE clause, i.e. it doesn't + * have a target reference at all. + */ + if (cur_ec->ec_sortref == 0 && sortref > 0) + cur_ec->ec_sortref = sortref; + return cur_ec; + } } } diff --git a/src/backend/optimizer/path/pathkeys.c b/src/backend/optimizer/path/pathkeys.c index ca94a31f71e..5aac6d66776 100644 --- a/src/backend/optimizer/path/pathkeys.c +++ b/src/backend/optimizer/path/pathkeys.c @@ -22,12 +22,15 @@ #include "nodes/makefuncs.h" #include "nodes/nodeFuncs.h" #include "nodes/plannodes.h" +#include "optimizer/cost.h" #include "optimizer/optimizer.h" #include "optimizer/pathnode.h" #include "optimizer/paths.h" #include "partitioning/partbounds.h" #include "utils/lsyscache.h" +/* Consider reordering of GROUP BY keys? */ +bool enable_group_by_reordering = true; static bool pathkey_is_redundant(PathKey *new_pathkey, List *pathkeys); static bool matches_boolean_partition_clause(RestrictInfo *rinfo, @@ -350,6 +353,170 @@ pathkeys_contained_in(List *keys1, List *keys2) return false; } +/* + * group_keys_reorder_by_pathkeys + * Reorder GROUP BY keys to match the input pathkeys. + * + * Function returns new lists (pathkeys and clauses), original GROUP BY lists + * stay untouched. + * + * Returns the number of GROUP BY keys with a matching pathkey. + */ +static int +group_keys_reorder_by_pathkeys(List *pathkeys, List **group_pathkeys, + List **group_clauses, + int num_groupby_pathkeys) +{ + List *new_group_pathkeys = NIL, + *new_group_clauses = NIL; + ListCell *lc; + int n; + + if (pathkeys == NIL || *group_pathkeys == NIL) + return 0; + + /* + * Walk the pathkeys (determining ordering of the input path) and see if + * there's a matching GROUP BY key. If we find one, we append it to the + * list, and do the same for the clauses. + * + * Once we find the first pathkey without a matching GROUP BY key, the + * rest of the pathkeys are useless and can't be used to evaluate the + * grouping, so we abort the loop and ignore the remaining pathkeys. + */ + foreach(lc, pathkeys) + { + PathKey *pathkey = (PathKey *) lfirst(lc); + SortGroupClause *sgc; + + /* + * Pathkeys are built in a way that allows simply comparing pointers. + * Give up if we can't find the matching pointer. + */ + if (foreach_current_index(lc) >= num_groupby_pathkeys || + !list_member_ptr(*group_pathkeys, pathkey)) + break; + + /* + * Since 1349d27 pathkey coming from underlying node can be in the + * root->group_pathkeys but not in the processed_groupClause. So, we + * should be careful here. + */ + sgc = get_sortgroupref_clause_noerr(pathkey->pk_eclass->ec_sortref, + *group_clauses); + if (!sgc) + /* The grouping clause does not cover this pathkey */ + break; + + new_group_pathkeys = lappend(new_group_pathkeys, pathkey); + new_group_clauses = lappend(new_group_clauses, sgc); + } + + /* remember the number of pathkeys with a matching GROUP BY key */ + n = list_length(new_group_pathkeys); + + /* append the remaining group pathkeys (will be treated as not sorted) */ + *group_pathkeys = list_concat_unique_ptr(new_group_pathkeys, + *group_pathkeys); + *group_clauses = list_concat_unique_ptr(new_group_clauses, + *group_clauses); + + return n; +} + +/* + * get_useful_group_keys_orderings + * Determine which orderings of GROUP BY keys are potentially interesting. + * + * Returns a list of PathKeyInfo items, each representing an interesting + * ordering of GROUP BY keys. Each item stores pathkeys and clauses in the + * matching order. + * + * The function considers (and keeps) multiple GROUP BY orderings: + * + * - the original ordering, as specified by the GROUP BY clause, + * - GROUP BY keys reordered to match 'path' ordering (as much as possible), + * - GROUP BY keys to match target ORDER BY clause (as much as possible). + */ +List * +get_useful_group_keys_orderings(PlannerInfo *root, Path *path) +{ + Query *parse = root->parse; + List *infos = NIL; + PathKeyInfo *info; + + List *pathkeys = root->group_pathkeys; + List *clauses = root->processed_groupClause; + + /* always return at least the original pathkeys/clauses */ + info = makeNode(PathKeyInfo); + info->pathkeys = pathkeys; + info->clauses = clauses; + infos = lappend(infos, info); + + /* + * Should we try generating alternative orderings of the group keys? If + * not, we produce only the order specified in the query, i.e. the + * optimization is effectively disabled. + */ + if (!enable_group_by_reordering) + return infos; + + /* + * Grouping sets have own and more complex logic to decide the ordering. + */ + if (parse->groupingSets) + return infos; + + /* + * If the path is sorted in some way, try reordering the group keys to + * match the path as much of the ordering as possible. Then thanks to + * incremental sort we would get this sort as cheap as possible. + */ + if (path->pathkeys) + { + int n; + + n = group_keys_reorder_by_pathkeys(path->pathkeys, &pathkeys, &clauses, + root->num_groupby_pathkeys); + + if (n > 0 && + (enable_incremental_sort || n == list_length(path->pathkeys))) + { + info = makeNode(PathKeyInfo); + info->pathkeys = pathkeys; + info->clauses = clauses; + + infos = lappend(infos, info); + } + } + + /* + * Try reordering pathkeys to minimize the sort cost (this time consider + * the ORDER BY clause). + */ + if (root->sort_pathkeys) + { + int n; + + n = group_keys_reorder_by_pathkeys(root->sort_pathkeys, &pathkeys, + &clauses, + root->num_groupby_pathkeys); + + if (n > 0 && + (enable_incremental_sort || n == list_length(path->pathkeys))) + { + info = makeNode(PathKeyInfo); + info->pathkeys = pathkeys; + info->clauses = clauses; + + infos = lappend(infos, info); + } + } + + return infos; +} + /* * pathkeys_count_contained_in * Same as pathkeys_contained_in, but also sets length of longest @@ -1939,6 +2106,54 @@ pathkeys_useful_for_ordering(PlannerInfo *root, List *pathkeys) return n_common_pathkeys; } +/* + * pathkeys_useful_for_grouping + * Count the number of pathkeys that are useful for grouping (instead of + * explicit sort) + * + * Group pathkeys could be reordered to benefit from the ordering. The + * ordering may not be "complete" and may require incremental sort, but that's + * fine. So we simply count prefix pathkeys with a matching group key, and + * stop once we find the first pathkey without a match. + * + * So e.g. with pathkeys (a,b,c) and group keys (a,b,e) this determines (a,b) + * pathkeys are useful for grouping, and we might do incremental sort to get + * path ordered by (a,b,e). + * + * This logic is necessary to retain paths with ordering not matching grouping + * keys directly, without the reordering. + * + * Returns the length of pathkey prefix with matching group keys. + */ +static int +pathkeys_useful_for_grouping(PlannerInfo *root, List *pathkeys) +{ + ListCell *key; + int n = 0; + + /* no special ordering requested for grouping */ + if (root->group_pathkeys == NIL) + return 0; + + /* unordered path */ + if (pathkeys == NIL) + return 0; + + /* walk the pathkeys and search for matching group key */ + foreach(key, pathkeys) + { + PathKey *pathkey = (PathKey *) lfirst(key); + + /* no matching group key, we're done */ + if (!list_member_ptr(root->group_pathkeys, pathkey)) + break; + + n++; + } + + return n; +} + /* * truncate_useless_pathkeys * Shorten the given pathkey list to just the useful pathkeys. @@ -1953,6 +2168,9 @@ truncate_useless_pathkeys(PlannerInfo *root, nuseful = pathkeys_useful_for_merging(root, rel, pathkeys); nuseful2 = pathkeys_useful_for_ordering(root, pathkeys); + if (nuseful2 > nuseful) + nuseful = nuseful2; + nuseful2 = pathkeys_useful_for_grouping(root, pathkeys); if (nuseful2 > nuseful) nuseful = nuseful2; @@ -1988,6 +2206,8 @@ has_useful_pathkeys(PlannerInfo *root, RelOptInfo *rel) { if (rel->joininfo != NIL || rel->has_eclass_joins) return true; /* might be able to use pathkeys for merging */ + if (root->group_pathkeys != NIL) + return true; /* might be able to use pathkeys for grouping */ if (root->query_pathkeys != NIL) return true; /* might be able to use them for ordering */ return false; /* definitely useless */ diff --git a/src/backend/optimizer/plan/planner.c b/src/backend/optimizer/plan/planner.c index 014b179c3f0..239b799a6b2 100644 --- a/src/backend/optimizer/plan/planner.c +++ b/src/backend/optimizer/plan/planner.c @@ -2805,8 +2805,9 @@ remove_useless_groupby_columns(PlannerInfo *root) * * In principle it might be interesting to consider other orderings of the * GROUP BY elements, which could match the sort ordering of other - * possible plans (eg an indexscan) and thereby reduce cost. We don't - * bother with that, though. Hashed grouping will frequently win anyway. + * possible plans (eg an indexscan) and thereby reduce cost. However, we + * don't yet have sufficient information to do that here, so that's left until + * later in planning. See get_useful_group_keys_orderings(). * * Note: we need no comparable processing of the distinctClause because * the parser already enforced that that matches ORDER BY. @@ -6891,103 +6892,135 @@ add_paths_to_grouping_rel(PlannerInfo *root, RelOptInfo *input_rel, */ foreach(lc, input_rel->pathlist) { + ListCell *lc2; Path *path = (Path *) lfirst(lc); + Path *path_save = path; + List *pathkey_orderings = NIL; - path = make_ordered_path(root, - grouped_rel, - path, - cheapest_path, - root->group_pathkeys); + /* generate alternative group orderings that might be useful */ + pathkey_orderings = get_useful_group_keys_orderings(root, path); - if (path == NULL) - continue; + Assert(list_length(pathkey_orderings) > 0); - /* Now decide what to stick atop it */ - if (parse->groupingSets) - { - consider_groupingsets_paths(root, grouped_rel, - path, true, can_hash, - gd, agg_costs, dNumGroups); - } - else if (parse->hasAggs) - { - /* - * We have aggregation, possibly with plain GROUP BY. Make an - * AggPath. - */ - add_path(grouped_rel, (Path *) - create_agg_path(root, - grouped_rel, - path, - grouped_rel->reltarget, - parse->groupClause ? AGG_SORTED : AGG_PLAIN, - AGGSPLIT_SIMPLE, - root->processed_groupClause, - havingQual, - agg_costs, - dNumGroups)); - } - else if (parse->groupClause) + foreach(lc2, pathkey_orderings) { - /* - * We have GROUP BY without aggregation or grouping sets. Make - * a GroupPath. - */ - add_path(grouped_rel, (Path *) - create_group_path(root, - grouped_rel, - path, - root->processed_groupClause, - havingQual, - dNumGroups)); - } - else - { - /* Other cases should have been handled above */ - Assert(false); - } - } + PathKeyInfo *info = (PathKeyInfo *) lfirst(lc2); - /* - * Instead of operating directly on the input relation, we can - * consider finalizing a partially aggregated path. - */ - if (partially_grouped_rel != NULL) - { - foreach(lc, partially_grouped_rel->pathlist) - { - Path *path = (Path *) lfirst(lc); + /* restore the path (we replace it in the loop) */ + path = path_save; path = make_ordered_path(root, grouped_rel, path, - partially_grouped_rel->cheapest_total_path, - root->group_pathkeys); - + cheapest_path, + info->pathkeys); if (path == NULL) continue; - if (parse->hasAggs) + /* Now decide what to stick atop it */ + if (parse->groupingSets) + { + consider_groupingsets_paths(root, grouped_rel, + path, true, can_hash, + gd, agg_costs, dNumGroups); + } + else if (parse->hasAggs) + { + /* + * We have aggregation, possibly with plain GROUP BY. Make + * an AggPath. + */ add_path(grouped_rel, (Path *) create_agg_path(root, grouped_rel, path, grouped_rel->reltarget, parse->groupClause ? AGG_SORTED : AGG_PLAIN, - AGGSPLIT_FINAL_DESERIAL, - root->processed_groupClause, + AGGSPLIT_SIMPLE, + info->clauses, havingQual, - agg_final_costs, + agg_costs, dNumGroups)); - else + } + else if (parse->groupClause) + { + /* + * We have GROUP BY without aggregation or grouping sets. + * Make a GroupPath. + */ add_path(grouped_rel, (Path *) create_group_path(root, grouped_rel, path, - root->processed_groupClause, + info->clauses, havingQual, dNumGroups)); + } + else + { + /* Other cases should have been handled above */ + Assert(false); + } + } + } + + /* + * Instead of operating directly on the input relation, we can + * consider finalizing a partially aggregated path. + */ + if (partially_grouped_rel != NULL) + { + foreach(lc, partially_grouped_rel->pathlist) + { + ListCell *lc2; + Path *path = (Path *) lfirst(lc); + Path *path_save = path; + List *pathkey_orderings = NIL; + + /* generate alternative group orderings that might be useful */ + pathkey_orderings = get_useful_group_keys_orderings(root, path); + + Assert(list_length(pathkey_orderings) > 0); + + /* process all potentially interesting grouping reorderings */ + foreach(lc2, pathkey_orderings) + { + PathKeyInfo *info = (PathKeyInfo *) lfirst(lc2); + /* restore the path (we replace it in the loop) */ + path = path_save; + + path = make_ordered_path(root, + grouped_rel, + path, + partially_grouped_rel->cheapest_total_path, + info->pathkeys); + + if (path == NULL) + continue; + + if (parse->hasAggs) + add_path(grouped_rel, (Path *) + create_agg_path(root, + grouped_rel, + path, + grouped_rel->reltarget, + parse->groupClause ? AGG_SORTED : AGG_PLAIN, + AGGSPLIT_FINAL_DESERIAL, + info->clauses, + havingQual, + agg_final_costs, + dNumGroups)); + else + add_path(grouped_rel, (Path *) + create_group_path(root, + grouped_rel, + path, + info->clauses, + havingQual, + dNumGroups)); + + } } } } @@ -7190,37 +7223,54 @@ create_partial_grouping_paths(PlannerInfo *root, */ foreach(lc, input_rel->pathlist) { + ListCell *lc2; Path *path = (Path *) lfirst(lc); + Path *path_save = path; + List *pathkey_orderings = NIL; - path = make_ordered_path(root, - partially_grouped_rel, - path, - cheapest_total_path, - root->group_pathkeys); + /* generate alternative group orderings that might be useful */ + pathkey_orderings = get_useful_group_keys_orderings(root, path); - if (path == NULL) - continue; + Assert(list_length(pathkey_orderings) > 0); - if (parse->hasAggs) - add_path(partially_grouped_rel, (Path *) - create_agg_path(root, + /* process all potentially interesting grouping reorderings */ + foreach(lc2, pathkey_orderings) + { + PathKeyInfo *info = (PathKeyInfo *) lfirst(lc2); + + /* restore the path (we replace it in the loop) */ + path = path_save; + + path = make_ordered_path(root, partially_grouped_rel, path, - partially_grouped_rel->reltarget, - parse->groupClause ? AGG_SORTED : AGG_PLAIN, - AGGSPLIT_INITIAL_SERIAL, - root->processed_groupClause, - NIL, - agg_partial_costs, - dNumPartialGroups)); - else - add_path(partially_grouped_rel, (Path *) - create_group_path(root, - partially_grouped_rel, - path, - root->processed_groupClause, - NIL, - dNumPartialGroups)); + cheapest_total_path, + info->pathkeys); + + if (path == NULL) + continue; + + if (parse->hasAggs) + add_path(partially_grouped_rel, (Path *) + create_agg_path(root, + partially_grouped_rel, + path, + partially_grouped_rel->reltarget, + parse->groupClause ? AGG_SORTED : AGG_PLAIN, + AGGSPLIT_INITIAL_SERIAL, + info->clauses, + NIL, + agg_partial_costs, + dNumPartialGroups)); + else + add_path(partially_grouped_rel, (Path *) + create_group_path(root, + partially_grouped_rel, + path, + info->clauses, + NIL, + dNumPartialGroups)); + } } } @@ -7229,37 +7279,55 @@ create_partial_grouping_paths(PlannerInfo *root, /* Similar to above logic, but for partial paths. */ foreach(lc, input_rel->partial_pathlist) { + ListCell *lc2; Path *path = (Path *) lfirst(lc); + Path *path_save = path; + List *pathkey_orderings = NIL; - path = make_ordered_path(root, - partially_grouped_rel, - path, - cheapest_partial_path, - root->group_pathkeys); + /* generate alternative group orderings that might be useful */ + pathkey_orderings = get_useful_group_keys_orderings(root, path); - if (path == NULL) - continue; + Assert(list_length(pathkey_orderings) > 0); - if (parse->hasAggs) - add_partial_path(partially_grouped_rel, (Path *) - create_agg_path(root, - partially_grouped_rel, - path, - partially_grouped_rel->reltarget, - parse->groupClause ? AGG_SORTED : AGG_PLAIN, - AGGSPLIT_INITIAL_SERIAL, - root->processed_groupClause, - NIL, - agg_partial_costs, - dNumPartialPartialGroups)); - else - add_partial_path(partially_grouped_rel, (Path *) - create_group_path(root, - partially_grouped_rel, - path, - root->processed_groupClause, - NIL, - dNumPartialPartialGroups)); + /* process all potentially interesting grouping reorderings */ + foreach(lc2, pathkey_orderings) + { + PathKeyInfo *info = (PathKeyInfo *) lfirst(lc2); + + + /* restore the path (we replace it in the loop) */ + path = path_save; + + path = make_ordered_path(root, + partially_grouped_rel, + path, + cheapest_partial_path, + info->pathkeys); + + if (path == NULL) + continue; + + if (parse->hasAggs) + add_partial_path(partially_grouped_rel, (Path *) + create_agg_path(root, + partially_grouped_rel, + path, + partially_grouped_rel->reltarget, + parse->groupClause ? AGG_SORTED : AGG_PLAIN, + AGGSPLIT_INITIAL_SERIAL, + info->clauses, + NIL, + agg_partial_costs, + dNumPartialPartialGroups)); + else + add_partial_path(partially_grouped_rel, (Path *) + create_group_path(root, + partially_grouped_rel, + path, + info->clauses, + NIL, + dNumPartialPartialGroups)); + } } } @@ -7373,6 +7441,8 @@ gather_grouping_paths(PlannerInfo *root, RelOptInfo *rel) * We can also skip the entire loop when we only have a single-item * group_pathkeys because then we can't possibly have a presorted prefix * of the list without having the list be fully sorted. + * + * XXX Shouldn't this also consider the group-key-reordering? */ if (!enable_incremental_sort || list_length(root->group_pathkeys) == 1) return; diff --git a/src/backend/utils/misc/guc_tables.c b/src/backend/utils/misc/guc_tables.c index e53ebc6dc2b..7fe58518d7d 100644 --- a/src/backend/utils/misc/guc_tables.c +++ b/src/backend/utils/misc/guc_tables.c @@ -1050,6 +1050,16 @@ struct config_bool ConfigureNamesBool[] = true, NULL, NULL, NULL }, + { + {"enable_group_by_reordering", PGC_USERSET, QUERY_TUNING_METHOD, + gettext_noop("Enables reordering of GROUP BY keys."), + NULL, + GUC_EXPLAIN + }, + &enable_group_by_reordering, + true, + NULL, NULL, NULL + }, { {"geqo", PGC_USERSET, QUERY_TUNING_GEQO, gettext_noop("Enables genetic query optimization."), diff --git a/src/backend/utils/misc/postgresql.conf.sample b/src/backend/utils/misc/postgresql.conf.sample index 835b0e9ba89..da10b43dac3 100644 --- a/src/backend/utils/misc/postgresql.conf.sample +++ b/src/backend/utils/misc/postgresql.conf.sample @@ -399,6 +399,7 @@ #enable_seqscan = on #enable_sort = on #enable_tidscan = on +#enable_group_by_reordering = on # - Planner Cost Constants - diff --git a/src/include/nodes/pathnodes.h b/src/include/nodes/pathnodes.h index b9713ec9aa6..137da178dc7 100644 --- a/src/include/nodes/pathnodes.h +++ b/src/include/nodes/pathnodes.h @@ -1456,6 +1456,16 @@ typedef struct PathKey bool pk_nulls_first; /* do NULLs come before normal values? */ } PathKey; +/* + * Combines the information about pathkeys and the associated clauses. + */ +typedef struct PathKeyInfo +{ + NodeTag type; + List *pathkeys; + List *clauses; +} PathKeyInfo; + /* * VolatileFunctionStatus -- allows nodes to cache their * contain_volatile_functions properties. VOLATILITY_UNKNOWN means not yet diff --git a/src/include/optimizer/paths.h b/src/include/optimizer/paths.h index efd4abc28f3..0e8a9c94ba6 100644 --- a/src/include/optimizer/paths.h +++ b/src/include/optimizer/paths.h @@ -24,6 +24,7 @@ extern PGDLLIMPORT bool enable_geqo; extern PGDLLIMPORT int geqo_threshold; extern PGDLLIMPORT int min_parallel_table_scan_size; extern PGDLLIMPORT int min_parallel_index_scan_size; +extern PGDLLIMPORT bool enable_group_by_reordering; /* Hook for plugins to get control in set_rel_pathlist() */ typedef void (*set_rel_pathlist_hook_type) (PlannerInfo *root, @@ -204,6 +205,7 @@ typedef enum extern PathKeysComparison compare_pathkeys(List *keys1, List *keys2); extern bool pathkeys_contained_in(List *keys1, List *keys2); extern bool pathkeys_count_contained_in(List *keys1, List *keys2, int *n_common); +extern List *get_useful_group_keys_orderings(PlannerInfo *root, Path *path); extern Path *get_cheapest_path_for_pathkeys(List *paths, List *pathkeys, Relids required_outer, CostSelector cost_criterion, diff --git a/src/test/regress/expected/aggregates.out b/src/test/regress/expected/aggregates.out index f635c5a1afb..0d46e096e5a 100644 --- a/src/test/regress/expected/aggregates.out +++ b/src/test/regress/expected/aggregates.out @@ -2728,6 +2728,160 @@ SELECT balk(hundred) FROM tenk1; (1 row) ROLLBACK; +-- GROUP BY optimization by reorder columns +CREATE TABLE btg AS SELECT + i % 100 AS x, + i % 100 AS y, + 'abc' || i % 10 AS z, + i AS w +FROM generate_series(1,10000) AS i; +CREATE INDEX abc ON btg(x,y); +ANALYZE btg; +-- GROUP BY optimization by reorder columns by frequency +SET enable_hashagg=off; +SET max_parallel_workers= 0; +SET max_parallel_workers_per_gather = 0; +-- Utilize index scan ordering to avoid a Sort operation +EXPLAIN (COSTS OFF) SELECT count(*) FROM btg GROUP BY x,y; + QUERY PLAN +---------------------------------------- + GroupAggregate + Group Key: x, y + -> Index Only Scan using abc on btg +(3 rows) + +EXPLAIN (COSTS OFF) SELECT count(*) FROM btg GROUP BY y,x; + QUERY PLAN +---------------------------------------- + GroupAggregate + Group Key: x, y + -> Index Only Scan using abc on btg +(3 rows) + +-- Engage incremental sort +explain (COSTS OFF) SELECT x,y FROM btg GROUP BY x,y,z,w; + QUERY PLAN +----------------------------------------- + Group + Group Key: x, y, z, w + -> Incremental Sort + Sort Key: x, y, z, w + Presorted Key: x, y + -> Index Scan using abc on btg +(6 rows) + +explain (COSTS OFF) SELECT x,y FROM btg GROUP BY z,y,w,x; + QUERY PLAN +----------------------------------------- + Group + Group Key: x, y, z, w + -> Incremental Sort + Sort Key: x, y, z, w + Presorted Key: x, y + -> Index Scan using abc on btg +(6 rows) + +explain (COSTS OFF) SELECT x,y FROM btg GROUP BY w,z,x,y; + QUERY PLAN +----------------------------------------- + Group + Group Key: x, y, w, z + -> Incremental Sort + Sort Key: x, y, w, z + Presorted Key: x, y + -> Index Scan using abc on btg +(6 rows) + +explain (COSTS OFF) SELECT x,y FROM btg GROUP BY w,x,z,y; + QUERY PLAN +----------------------------------------- + Group + Group Key: x, y, w, z + -> Incremental Sort + Sort Key: x, y, w, z + Presorted Key: x, y + -> Index Scan using abc on btg +(6 rows) + +-- Subqueries +explain (COSTS OFF) SELECT x,y +FROM (SELECT * FROM btg ORDER BY x,y,w,z) AS q1 +GROUP BY (w,x,z,y); + QUERY PLAN +---------------------------------------------- + Group + Group Key: btg.x, btg.y, btg.w, btg.z + -> Incremental Sort + Sort Key: btg.x, btg.y, btg.w, btg.z + Presorted Key: btg.x, btg.y + -> Index Scan using abc on btg +(6 rows) + +explain (COSTS OFF) SELECT x,y +FROM (SELECT * FROM btg ORDER BY x,y,w,z LIMIT 100) AS q1 +GROUP BY (w,x,z,y); + QUERY PLAN +---------------------------------------------------- + Group + Group Key: btg.x, btg.y, btg.w, btg.z + -> Limit + -> Incremental Sort + Sort Key: btg.x, btg.y, btg.w, btg.z + Presorted Key: btg.x, btg.y + -> Index Scan using abc on btg +(7 rows) + +-- Should work with and without GROUP-BY optimization +explain (COSTS OFF) SELECT x,y FROM btg GROUP BY w,x,z,y ORDER BY y,x,z,w; + QUERY PLAN +------------------------------ + Group + Group Key: y, x, z, w + -> Sort + Sort Key: y, x, z, w + -> Seq Scan on btg +(5 rows) + +-- Utilize incremental sort to make the ORDER BY rule a bit cheaper +explain (COSTS OFF) SELECT x,w FROM btg GROUP BY w,x,y,z ORDER BY x*x,z; + QUERY PLAN +----------------------------------------------- + Sort + Sort Key: ((x * x)), z + -> Group + Group Key: x, y, w, z + -> Incremental Sort + Sort Key: x, y, w, z + Presorted Key: x, y + -> Index Scan using abc on btg +(8 rows) + +DROP TABLE btg; +-- The case, when scanning sort order correspond to aggregate sort order but +-- can not be found in the group-by list +CREATE TABLE t1 (c1 int PRIMARY KEY, c2 int); +CREATE UNIQUE INDEX ON t1(c2); +explain (costs off) +SELECT array_agg(c1 ORDER BY c2),c2 +FROM t1 WHERE c2 < 100 GROUP BY c1 ORDER BY 2; + QUERY PLAN +-------------------------------------------------------- + Sort + Sort Key: c2 + -> GroupAggregate + Group Key: c1 + -> Sort + Sort Key: c1, c2 + -> Bitmap Heap Scan on t1 + Recheck Cond: (c2 < 100) + -> Bitmap Index Scan on t1_c2_idx + Index Cond: (c2 < 100) +(10 rows) + +DROP TABLE t1 CASCADE; +RESET enable_hashagg; +RESET max_parallel_workers; +RESET max_parallel_workers_per_gather; -- Secondly test the case of a parallel aggregate combiner function -- returning NULL. For that use normal transition function, but a -- combiner function returning NULL. diff --git a/src/test/regress/expected/sysviews.out b/src/test/regress/expected/sysviews.out index 271313ebf86..9be7aca2b8a 100644 --- a/src/test/regress/expected/sysviews.out +++ b/src/test/regress/expected/sysviews.out @@ -114,6 +114,7 @@ select name, setting from pg_settings where name like 'enable%'; enable_async_append | on enable_bitmapscan | on enable_gathermerge | on + enable_group_by_reordering | on enable_hashagg | on enable_hashjoin | on enable_incremental_sort | on @@ -133,7 +134,7 @@ select name, setting from pg_settings where name like 'enable%'; enable_seqscan | on enable_sort | on enable_tidscan | on -(22 rows) +(23 rows) -- There are always wait event descriptions for various types. select type, count(*) > 0 as ok FROM pg_wait_events diff --git a/src/test/regress/sql/aggregates.sql b/src/test/regress/sql/aggregates.sql index cc8f0efad55..f99167ac9ea 100644 --- a/src/test/regress/sql/aggregates.sql +++ b/src/test/regress/sql/aggregates.sql @@ -1181,6 +1181,62 @@ SELECT balk(hundred) FROM tenk1; ROLLBACK; +-- GROUP BY optimization by reorder columns + +CREATE TABLE btg AS SELECT + i % 100 AS x, + i % 100 AS y, + 'abc' || i % 10 AS z, + i AS w +FROM generate_series(1,10000) AS i; +CREATE INDEX abc ON btg(x,y); +ANALYZE btg; + +-- GROUP BY optimization by reorder columns by frequency + +SET enable_hashagg=off; +SET max_parallel_workers= 0; +SET max_parallel_workers_per_gather = 0; + +-- Utilize index scan ordering to avoid a Sort operation +EXPLAIN (COSTS OFF) SELECT count(*) FROM btg GROUP BY x,y; +EXPLAIN (COSTS OFF) SELECT count(*) FROM btg GROUP BY y,x; + +-- Engage incremental sort +explain (COSTS OFF) SELECT x,y FROM btg GROUP BY x,y,z,w; +explain (COSTS OFF) SELECT x,y FROM btg GROUP BY z,y,w,x; +explain (COSTS OFF) SELECT x,y FROM btg GROUP BY w,z,x,y; +explain (COSTS OFF) SELECT x,y FROM btg GROUP BY w,x,z,y; + +-- Subqueries +explain (COSTS OFF) SELECT x,y +FROM (SELECT * FROM btg ORDER BY x,y,w,z) AS q1 +GROUP BY (w,x,z,y); +explain (COSTS OFF) SELECT x,y +FROM (SELECT * FROM btg ORDER BY x,y,w,z LIMIT 100) AS q1 +GROUP BY (w,x,z,y); + +-- Should work with and without GROUP-BY optimization +explain (COSTS OFF) SELECT x,y FROM btg GROUP BY w,x,z,y ORDER BY y,x,z,w; + +-- Utilize incremental sort to make the ORDER BY rule a bit cheaper +explain (COSTS OFF) SELECT x,w FROM btg GROUP BY w,x,y,z ORDER BY x*x,z; + +DROP TABLE btg; + +-- The case, when scanning sort order correspond to aggregate sort order but +-- can not be found in the group-by list +CREATE TABLE t1 (c1 int PRIMARY KEY, c2 int); +CREATE UNIQUE INDEX ON t1(c2); +explain (costs off) +SELECT array_agg(c1 ORDER BY c2),c2 +FROM t1 WHERE c2 < 100 GROUP BY c1 ORDER BY 2; +DROP TABLE t1 CASCADE; + +RESET enable_hashagg; +RESET max_parallel_workers; +RESET max_parallel_workers_per_gather; + -- Secondly test the case of a parallel aggregate combiner function -- returning NULL. For that use normal transition function, but a -- combiner function returning NULL. diff --git a/src/tools/pgindent/typedefs.list b/src/tools/pgindent/typedefs.list index f582eb59e7d..e575fa13c63 100644 --- a/src/tools/pgindent/typedefs.list +++ b/src/tools/pgindent/typedefs.list @@ -4041,3 +4041,4 @@ manifest_writer rfile ws_options ws_file_info +PathKeyInfo -- 2.39.3 (Apple Git-145)