From 340ae3cfb8f38a49664c0da3ff033346e92f0450 Mon Sep 17 00:00:00 2001 From: Heikki Linnakangas Date: Fri, 20 Nov 2020 14:41:14 +0200 Subject: [PATCH] Skip allocating hash table in EXPLAIN-only mode. This is a backpatch of commit 2cccb627f1, backpatched due to popular demand. Backpatch to all supported versions. Author: Alexey Bashtanov Discussion: https://www.postgresql.org/message-id/36823f65-050d-ae24-aa4d-a37726998240%40imap.cc --- src/backend/executor/nodeAgg.c | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-) diff --git a/src/backend/executor/nodeAgg.c b/src/backend/executor/nodeAgg.c index 75e5bbf209d..8a0bd887bf0 100644 --- a/src/backend/executor/nodeAgg.c +++ b/src/backend/executor/nodeAgg.c @@ -3665,7 +3665,11 @@ ExecInitAgg(Agg *node, EState *estate, int eflags) &aggstate->hash_ngroups_limit, &aggstate->hash_planned_partitions); find_hash_columns(aggstate); - build_hash_tables(aggstate); + + /* Skip massive memory allocation if we are just doing EXPLAIN */ + if (!(eflags & EXEC_FLAG_EXPLAIN_ONLY)) + build_hash_tables(aggstate); + aggstate->table_filled = false; /* Initialize this to 1, meaning nothing spilled, yet */