From 0041de71c24540a1b65b2ddd652bbb905b5937aa Mon Sep 17 00:00:00 2001 From: Tomas Vondra Date: Mon, 17 Jun 2024 16:19:16 +0200 Subject: [PATCH v20240617 30/56] optimize the order of mcv equal function evaluation using n_dinstinct values. See the test in ext_sort_mcv_proc.sql which should not be committed since it is just a manual test. --- src/backend/statistics/mcv.c | 100 ++++++++++++++------- src/test/regress/sql/ext_sort_mcv_proc.sql | 30 +++++++ 2 files changed, 97 insertions(+), 33 deletions(-) create mode 100644 src/test/regress/sql/ext_sort_mcv_proc.sql diff --git a/src/backend/statistics/mcv.c b/src/backend/statistics/mcv.c index 0db285a8958..96f4c1b94f6 100644 --- a/src/backend/statistics/mcv.c +++ b/src/backend/statistics/mcv.c @@ -72,6 +72,33 @@ ((ndims) * sizeof(DimensionInfo)) + \ ((nitems) * ITEM_SIZE(ndims))) +// #define DEBUG_MCV 1 /* should be removed after review. */ + +typedef struct +{ + FmgrInfo fmgrinfo; + FunctionCallInfo fcinfo; + double n_distinct; +#ifdef DEBUG_MCV + int idx; +#endif +} McvProc; + +static int +cmp_mcv_proc(const void *a, const void *b) +{ + /* sort the McvProc reversely based on n_distinct value. */ + McvProc *m1 = (McvProc *) a; + McvProc *m2 = (McvProc *) b; + + if (m1->n_distinct > m2->n_distinct) + return -1; + else if (m1->n_distinct == m2->n_distinct) + return 0; + else + return 1; +} + static MultiSortSupport build_mss(StatsBuildData *data); static SortItem *build_distinct_groups(int numrows, SortItem *items, @@ -2246,8 +2273,7 @@ mcv_combine_extended(PlannerInfo *root, RelOptInfo *rel1, RelOptInfo *rel2, totalsel2; /* info about clauses and how they match to MCV stats */ - FmgrInfo *finfo; - FunctionCallInfo *opprocs; + McvProc *mcvProc; int *indexes1, *indexes2; bool *reverse; @@ -2295,14 +2321,7 @@ mcv_combine_extended(PlannerInfo *root, RelOptInfo *rel1, RelOptInfo *rel2, * stats we picked. We do this only once before processing the lists, so * that we don't have to do that for each MCV item or so. */ - finfo = (FmgrInfo *) palloc(sizeof(FmgrInfo) * list_length(clauses)); - /* FIXME remove? */ - - /* - * opprocs = (FunctionCallInfo *) palloc(SizeForFunctionCallInfo(2) * - * list_length(clauses)); - */ - opprocs = (FunctionCallInfo *) palloc(sizeof(FunctionCallInfo *) * list_length(clauses)); + mcvProc = (McvProc *) palloc(sizeof(McvProc) * list_length(clauses)); indexes1 = (int *) palloc(sizeof(int) * list_length(clauses)); indexes2 = (int *) palloc(sizeof(int) * list_length(clauses)); reverse = (bool *) palloc(sizeof(bool) * list_length(clauses)); @@ -2325,6 +2344,9 @@ mcv_combine_extended(PlannerInfo *root, RelOptInfo *rel1, RelOptInfo *rel2, *expr2; int idx = list_cell_number(clauses, lc); FunctionCallInfo fcinfo = palloc(SizeForFunctionCallInfo(2)); + VariableStatData vardata; + bool isdefault; + Node *left_expr; opexpr = (OpExpr *) clause; @@ -2332,17 +2354,18 @@ mcv_combine_extended(PlannerInfo *root, RelOptInfo *rel1, RelOptInfo *rel2, Assert(is_opclause(clause)); Assert(list_length(opexpr->args) == 2); - fmgr_info(get_opcode(opexpr->opno), &finfo[idx]); - - InitFunctionCallInfoData(*fcinfo, &finfo[idx], + fmgr_info(get_opcode(opexpr->opno), &mcvProc[idx].fmgrinfo); + mcvProc[idx].fcinfo = fcinfo; +#ifdef DEBUG_MCV + mcvProc[idx].idx = idx; +#endif + InitFunctionCallInfoData(*mcvProc[idx].fcinfo, + &mcvProc[idx].fmgrinfo, 2, opexpr->inputcollid, NULL, NULL); fcinfo->args[0].isnull = false; fcinfo->args[1].isnull = false; - /* XXX Do we even need this, if we have finfo? */ - opprocs[idx] = fcinfo; - expr1 = linitial(opexpr->args); expr2 = lsecond(opexpr->args); @@ -2368,6 +2391,8 @@ mcv_combine_extended(PlannerInfo *root, RelOptInfo *rel1, RelOptInfo *rel2, exprs1 = lappend(exprs1, expr1); exprs2 = lappend(exprs2, expr2); + + left_expr = expr1; } else if ((bms_singleton_member(rinfo->right_relids) == rel1->relid) && (bms_singleton_member(rinfo->left_relids) == rel2->relid)) @@ -2384,6 +2409,8 @@ mcv_combine_extended(PlannerInfo *root, RelOptInfo *rel1, RelOptInfo *rel2, exprs1 = lappend(exprs1, expr2); exprs2 = lappend(exprs2, expr1); + + left_expr = expr2; } else /* should never happen */ @@ -2394,8 +2421,23 @@ mcv_combine_extended(PlannerInfo *root, RelOptInfo *rel1, RelOptInfo *rel2, Assert((indexes2[idx] >= 0) && (indexes2[idx] < bms_num_members(stat2->keys) + list_length(stat2->exprs))); + + examine_variable(root, left_expr, rel1->relid, &vardata); + mcvProc[idx].n_distinct = get_variable_numdistinct(&vardata, &isdefault); + // elog(INFO, "n_distinct = %f", mcvProc[idx].n_distinct); + ReleaseVariableStats(vardata); } + /* order the McvProc */ + pg_qsort(mcvProc, list_length(clauses), sizeof(McvProc), cmp_mcv_proc); + +#ifdef DEBUG_MCV + for (i = 0; i < list_length(clauses); i++) + { + elog(INFO, "%d", mcvProc[i].idx); + } +#endif + /* * Match items between the two MCV lists. * @@ -2451,23 +2493,17 @@ mcv_combine_extended(PlannerInfo *root, RelOptInfo *rel1, RelOptInfo *rel2, */ /* - * Evaluate if all the join clauses match between the two MCV - * items. - * - * XXX We might optimize the order of evaluation, using the costs - * of operator functions for individual columns. It does depend on - * the number of distinct values, etc. + * Evaluate if all the join clauses match between the two MCV items. */ - idx = 0; - foreach(lc, clauses) + for(idx = 0; idx < list_length(clauses); idx++) { - bool match; - int index1 = indexes1[idx], - index2 = indexes2[idx]; - Datum value1, - value2; - bool reverse_args = reverse[idx]; - FunctionCallInfo fcinfo = opprocs[idx]; + bool match; + int index1 = indexes1[idx], + index2 = indexes2[idx]; + Datum value1, + value2; + bool reverse_args = reverse[idx]; + FunctionCallInfo fcinfo = mcvProc[idx].fcinfo; /* If either value is null, it's a mismatch */ if (mcv2->items[j].isnull[index2]) @@ -2498,8 +2534,6 @@ mcv_combine_extended(PlannerInfo *root, RelOptInfo *rel1, RelOptInfo *rel2, if (!items_match) break; - - idx++; } if (items_match) diff --git a/src/test/regress/sql/ext_sort_mcv_proc.sql b/src/test/regress/sql/ext_sort_mcv_proc.sql new file mode 100644 index 00000000000..09360d5b23e --- /dev/null +++ b/src/test/regress/sql/ext_sort_mcv_proc.sql @@ -0,0 +1,30 @@ +create table t(level_1 text, level_2 text, level_3 text); + +insert into t +values +('l11', 'l21', 'l31'), +('l11', 'l21', 'l32'), +('l11', 'l21', 'l33'), +('l11', 'l22', 'l34'), +('l11', 'l22', 'l35'), +('l11', 'l22', 'l36'); + +create statistics on level_1, level_2, level_3 from t; + +analyze t; + +explain select * from t t1 join t t2 using(level_1, level_2, level_3); +INFO: n_distinct = 1.000000 +INFO: n_distinct = 2.000000 +INFO: n_distinct = 6.000000 +INFO: 2 +INFO: 1 +INFO: 0 + QUERY PLAN +------------------------------------------------------------------------------------------------------ + Hash Join (cost=1.17..2.32 rows=6 width=12) + Hash Cond: ((t1.level_1 = t2.level_1) AND (t1.level_2 = t2.level_2) AND (t1.level_3 = t2.level_3)) + -> Seq Scan on t t1 (cost=0.00..1.06 rows=6 width=12) + -> Hash (cost=1.06..1.06 rows=6 width=12) + -> Seq Scan on t t2 (cost=0.00..1.06 rows=6 width=12) +(5 rows) -- 2.45.2