From 7a8176b9eb9dd9982662d83b86996c5402378674 Mon Sep 17 00:00:00 2001 From: David Geier Date: Fri, 11 Nov 2022 12:33:11 +0100 Subject: [PATCH] Skip reading MCV stats for unique join attributes MCV stats are not stored for unique columns. If one of the two join attributes is unique, reading the MCV stats can be skipped for both columns because they are only ever used during join selectivity estimation if they're present on both attributes. --- src/backend/utils/adt/selfuncs.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) diff --git a/src/backend/utils/adt/selfuncs.c b/src/backend/utils/adt/selfuncs.c index d597b7e81f..3c9007c8d1 100644 --- a/src/backend/utils/adt/selfuncs.c +++ b/src/backend/utils/adt/selfuncs.c @@ -2263,6 +2263,7 @@ eqjoinsel(PG_FUNCTION_ARGS) bool have_mcvs2 = false; bool join_is_reversed; RelOptInfo *inner_rel; + bool get_mcv_stats; get_join_variables(root, args, sjinfo, &vardata1, &vardata2, &join_is_reversed); @@ -2270,6 +2271,7 @@ eqjoinsel(PG_FUNCTION_ARGS) nd1 = get_variable_numdistinct(&vardata1, &isdefault1); nd2 = get_variable_numdistinct(&vardata2, &isdefault2); + get_mcv_stats = !vardata1.isunique && !vardata2.isunique; opfuncoid = get_opcode(operator); memset(&sslot1, 0, sizeof(sslot1)); @@ -2279,7 +2281,7 @@ eqjoinsel(PG_FUNCTION_ARGS) { /* note we allow use of nullfrac regardless of security check */ stats1 = (Form_pg_statistic) GETSTRUCT(vardata1.statsTuple); - if (statistic_proc_security_check(&vardata1, opfuncoid)) + if (get_mcv_stats && statistic_proc_security_check(&vardata1, opfuncoid)) have_mcvs1 = get_attstatsslot(&sslot1, vardata1.statsTuple, STATISTIC_KIND_MCV, InvalidOid, ATTSTATSSLOT_VALUES | ATTSTATSSLOT_NUMBERS); @@ -2289,7 +2291,7 @@ eqjoinsel(PG_FUNCTION_ARGS) { /* note we allow use of nullfrac regardless of security check */ stats2 = (Form_pg_statistic) GETSTRUCT(vardata2.statsTuple); - if (statistic_proc_security_check(&vardata2, opfuncoid)) + if (get_mcv_stats && statistic_proc_security_check(&vardata2, opfuncoid)) have_mcvs2 = get_attstatsslot(&sslot2, vardata2.statsTuple, STATISTIC_KIND_MCV, InvalidOid, ATTSTATSSLOT_VALUES | ATTSTATSSLOT_NUMBERS); -- 2.34.1