diff --git a/doc/src/sgml/config.sgml b/doc/src/sgml/config.sgml
index 53b361e7a9..d99bf38e67 100644
--- a/doc/src/sgml/config.sgml
+++ b/doc/src/sgml/config.sgml
@@ -1849,9 +1849,8 @@ include_dir 'conf.d'
operations can use. The final limit is determined by
multiplying work_mem by
hash_mem_multiplier. The default value is
- 1.0, which makes hash-based operations subject to the same
- simple work_mem maximum as sort-based
- operations.
+ 2.0, which makes hash-based operations use twice the usual
+ work_mem base amount.
Consider increasing hash_mem_multiplier in
@@ -1859,7 +1858,7 @@ include_dir 'conf.d'
occurrence, especially when simply increasing
work_mem results in memory pressure (memory
pressure typically takes the form of intermittent out of
- memory errors). A setting of 1.5 or 2.0 may be effective with
+ memory errors). The default setting of 2.0 is often effective with
mixed workloads. Higher settings in the range of 2.0 - 8.0 or
more may be effective in environments where
work_mem has already been increased to 40MB
diff --git a/src/backend/utils/init/globals.c b/src/backend/utils/init/globals.c
index c26a1a73df..3419c099b2 100644
--- a/src/backend/utils/init/globals.c
+++ b/src/backend/utils/init/globals.c
@@ -122,7 +122,7 @@ int IntervalStyle = INTSTYLE_POSTGRES;
bool enableFsync = true;
bool allowSystemTableMods = false;
int work_mem = 4096;
-double hash_mem_multiplier = 1.0;
+double hash_mem_multiplier = 2.0;
int maintenance_work_mem = 65536;
int max_parallel_maintenance_workers = 2;
diff --git a/src/backend/utils/misc/guc.c b/src/backend/utils/misc/guc.c
index 9d0208ec98..01f373815e 100644
--- a/src/backend/utils/misc/guc.c
+++ b/src/backend/utils/misc/guc.c
@@ -3762,7 +3762,7 @@ static struct config_real ConfigureNamesReal[] =
GUC_EXPLAIN
},
&hash_mem_multiplier,
- 1.0, 1.0, 1000.0,
+ 2.0, 1.0, 1000.0,
NULL, NULL, NULL
},
diff --git a/src/backend/utils/misc/postgresql.conf.sample b/src/backend/utils/misc/postgresql.conf.sample
index 56d0bee6d9..4a094bb38b 100644
--- a/src/backend/utils/misc/postgresql.conf.sample
+++ b/src/backend/utils/misc/postgresql.conf.sample
@@ -136,7 +136,7 @@
# Caution: it is not advisable to set max_prepared_transactions nonzero unless
# you actively intend to use prepared transactions.
#work_mem = 4MB # min 64kB
-#hash_mem_multiplier = 1.0 # 1-1000.0 multiplier on hash table work_mem
+#hash_mem_multiplier = 2.0 # 1-1000.0 multiplier on hash table work_mem
#maintenance_work_mem = 64MB # min 1MB
#autovacuum_work_mem = -1 # min 1MB, or -1 to use maintenance_work_mem
#logical_decoding_work_mem = 64MB # min 64kB
diff --git a/src/test/regress/expected/groupingsets.out b/src/test/regress/expected/groupingsets.out
index 4c467c1b15..58a25b691a 100644
--- a/src/test/regress/expected/groupingsets.out
+++ b/src/test/regress/expected/groupingsets.out
@@ -1574,6 +1574,7 @@ select array(select row(v.a,s1.*) from (select two,four, count(*) from onek grou
-- test the knapsack
set enable_indexscan = false;
+set hash_mem_multiplier = 1.0;
set work_mem = '64kB';
explain (costs off)
select unique1,
@@ -1919,6 +1920,7 @@ select g100, g10, sum(g::numeric), count(*), max(g::text)
from gs_data_1 group by cube (g1000, g100,g10);
set enable_sort = true;
set work_mem to default;
+set hash_mem_multiplier to default;
-- Compare results
(select * from gs_hash_1 except select * from gs_group_1)
union all
diff --git a/src/test/regress/expected/join_hash.out b/src/test/regress/expected/join_hash.out
index 3a91c144a2..3ec07bc1af 100644
--- a/src/test/regress/expected/join_hash.out
+++ b/src/test/regress/expected/join_hash.out
@@ -86,6 +86,7 @@ alter table wide set (parallel_workers = 2);
savepoint settings;
set local max_parallel_workers_per_gather = 0;
set local work_mem = '4MB';
+set local hash_mem_multiplier = 1.0;
explain (costs off)
select count(*) from simple r join simple s using (id);
QUERY PLAN
@@ -119,6 +120,7 @@ rollback to settings;
savepoint settings;
set local max_parallel_workers_per_gather = 2;
set local work_mem = '4MB';
+set local hash_mem_multiplier = 1.0;
set local enable_parallel_hash = off;
explain (costs off)
select count(*) from simple r join simple s using (id);
@@ -156,6 +158,7 @@ rollback to settings;
savepoint settings;
set local max_parallel_workers_per_gather = 2;
set local work_mem = '4MB';
+set local hash_mem_multiplier = 1.0;
set local enable_parallel_hash = on;
explain (costs off)
select count(*) from simple r join simple s using (id);
@@ -196,6 +199,7 @@ rollback to settings;
savepoint settings;
set local max_parallel_workers_per_gather = 0;
set local work_mem = '128kB';
+set local hash_mem_multiplier = 1.0;
explain (costs off)
select count(*) from simple r join simple s using (id);
QUERY PLAN
@@ -229,6 +233,7 @@ rollback to settings;
savepoint settings;
set local max_parallel_workers_per_gather = 2;
set local work_mem = '128kB';
+set local hash_mem_multiplier = 1.0;
set local enable_parallel_hash = off;
explain (costs off)
select count(*) from simple r join simple s using (id);
@@ -266,6 +271,7 @@ rollback to settings;
savepoint settings;
set local max_parallel_workers_per_gather = 2;
set local work_mem = '192kB';
+set local hash_mem_multiplier = 1.0;
set local enable_parallel_hash = on;
explain (costs off)
select count(*) from simple r join simple s using (id);
@@ -307,6 +313,7 @@ rollback to settings;
savepoint settings;
set local max_parallel_workers_per_gather = 0;
set local work_mem = '128kB';
+set local hash_mem_multiplier = 1.0;
explain (costs off)
select count(*) FROM simple r JOIN bigger_than_it_looks s USING (id);
QUERY PLAN
@@ -340,6 +347,7 @@ rollback to settings;
savepoint settings;
set local max_parallel_workers_per_gather = 2;
set local work_mem = '128kB';
+set local hash_mem_multiplier = 1.0;
set local enable_parallel_hash = off;
explain (costs off)
select count(*) from simple r join bigger_than_it_looks s using (id);
@@ -377,6 +385,7 @@ rollback to settings;
savepoint settings;
set local max_parallel_workers_per_gather = 1;
set local work_mem = '192kB';
+set local hash_mem_multiplier = 1.0;
set local enable_parallel_hash = on;
explain (costs off)
select count(*) from simple r join bigger_than_it_looks s using (id);
@@ -419,6 +428,7 @@ rollback to settings;
savepoint settings;
set local max_parallel_workers_per_gather = 0;
set local work_mem = '128kB';
+set local hash_mem_multiplier = 1.0;
explain (costs off)
select count(*) from simple r join extremely_skewed s using (id);
QUERY PLAN
@@ -451,6 +461,7 @@ rollback to settings;
savepoint settings;
set local max_parallel_workers_per_gather = 2;
set local work_mem = '128kB';
+set local hash_mem_multiplier = 1.0;
set local enable_parallel_hash = off;
explain (costs off)
select count(*) from simple r join extremely_skewed s using (id);
@@ -486,6 +497,7 @@ rollback to settings;
savepoint settings;
set local max_parallel_workers_per_gather = 1;
set local work_mem = '128kB';
+set local hash_mem_multiplier = 1.0;
set local enable_parallel_hash = on;
explain (costs off)
select count(*) from simple r join extremely_skewed s using (id);
@@ -523,6 +535,7 @@ rollback to settings;
savepoint settings;
set local max_parallel_workers_per_gather = 2;
set local work_mem = '4MB';
+set local hash_mem_multiplier = 1.0;
set local parallel_leader_participation = off;
select * from hash_join_batches(
$$
@@ -551,6 +564,7 @@ set max_parallel_workers_per_gather = 2;
set enable_material = off;
set enable_mergejoin = off;
set work_mem = '64kB';
+set hash_mem_multiplier = 1.0;
explain (costs off)
select count(*) from join_foo
left join (select b1.id, b1.t from join_bar b1 join join_bar b2 using (id)) ss
@@ -602,6 +616,7 @@ set max_parallel_workers_per_gather = 2;
set enable_material = off;
set enable_mergejoin = off;
set work_mem = '4MB';
+set hash_mem_multiplier = 1.0;
explain (costs off)
select count(*) from join_foo
left join (select b1.id, b1.t from join_bar b1 join join_bar b2 using (id)) ss
@@ -653,6 +668,7 @@ set max_parallel_workers_per_gather = 2;
set enable_material = off;
set enable_mergejoin = off;
set work_mem = '64kB';
+set hash_mem_multiplier = 1.0;
explain (costs off)
select count(*) from join_foo
left join (select b1.id, b1.t from join_bar b1 join join_bar b2 using (id)) ss
@@ -704,6 +720,7 @@ set max_parallel_workers_per_gather = 2;
set enable_material = off;
set enable_mergejoin = off;
set work_mem = '4MB';
+set hash_mem_multiplier = 1.0;
explain (costs off)
select count(*) from join_foo
left join (select b1.id, b1.t from join_bar b1 join join_bar b2 using (id)) ss
@@ -843,6 +860,7 @@ savepoint settings;
set max_parallel_workers_per_gather = 2;
set enable_parallel_hash = on;
set work_mem = '128kB';
+set hash_mem_multiplier = 1.0;
explain (costs off)
select length(max(s.t))
from wide left join (select id, coalesce(t, '') || '' as t from wide) s using (id);
diff --git a/src/test/regress/expected/memoize.out b/src/test/regress/expected/memoize.out
index 4ca0bd1f1e..00438eb1ea 100644
--- a/src/test/regress/expected/memoize.out
+++ b/src/test/regress/expected/memoize.out
@@ -90,8 +90,9 @@ WHERE t1.unique1 < 1000;
1000 | 9.5000000000000000
(1 row)
--- Reduce work_mem so that we see some cache evictions
+-- Reduce work_mem and hash_mem_multiplier so that we see some cache evictions
SET work_mem TO '64kB';
+SET hash_mem_multiplier TO 1.0;
SET enable_mergejoin TO off;
-- Ensure we get some evictions. We're unable to validate the hits and misses
-- here as the number of entries that fit in the cache at once will vary
@@ -238,6 +239,7 @@ WHERE unique1 < 3
RESET enable_seqscan;
RESET enable_mergejoin;
RESET work_mem;
+RESET hash_mem_multiplier;
RESET enable_bitmapscan;
RESET enable_hashjoin;
-- Test parallel plans with Memoize
diff --git a/src/test/regress/sql/groupingsets.sql b/src/test/regress/sql/groupingsets.sql
index 3944944704..473d21f6b9 100644
--- a/src/test/regress/sql/groupingsets.sql
+++ b/src/test/regress/sql/groupingsets.sql
@@ -424,6 +424,7 @@ select array(select row(v.a,s1.*) from (select two,four, count(*) from onek grou
-- test the knapsack
set enable_indexscan = false;
+set hash_mem_multiplier = 1.0;
set work_mem = '64kB';
explain (costs off)
select unique1,
@@ -519,6 +520,7 @@ from gs_data_1 group by cube (g1000, g100,g10);
set enable_sort = true;
set work_mem to default;
+set hash_mem_multiplier to default;
-- Compare results
diff --git a/src/test/regress/sql/join_hash.sql b/src/test/regress/sql/join_hash.sql
index 68c1a8c7b6..77dbc182d5 100644
--- a/src/test/regress/sql/join_hash.sql
+++ b/src/test/regress/sql/join_hash.sql
@@ -95,6 +95,7 @@ alter table wide set (parallel_workers = 2);
savepoint settings;
set local max_parallel_workers_per_gather = 0;
set local work_mem = '4MB';
+set local hash_mem_multiplier = 1.0;
explain (costs off)
select count(*) from simple r join simple s using (id);
select count(*) from simple r join simple s using (id);
@@ -109,6 +110,7 @@ rollback to settings;
savepoint settings;
set local max_parallel_workers_per_gather = 2;
set local work_mem = '4MB';
+set local hash_mem_multiplier = 1.0;
set local enable_parallel_hash = off;
explain (costs off)
select count(*) from simple r join simple s using (id);
@@ -124,6 +126,7 @@ rollback to settings;
savepoint settings;
set local max_parallel_workers_per_gather = 2;
set local work_mem = '4MB';
+set local hash_mem_multiplier = 1.0;
set local enable_parallel_hash = on;
explain (costs off)
select count(*) from simple r join simple s using (id);
@@ -143,6 +146,7 @@ rollback to settings;
savepoint settings;
set local max_parallel_workers_per_gather = 0;
set local work_mem = '128kB';
+set local hash_mem_multiplier = 1.0;
explain (costs off)
select count(*) from simple r join simple s using (id);
select count(*) from simple r join simple s using (id);
@@ -157,6 +161,7 @@ rollback to settings;
savepoint settings;
set local max_parallel_workers_per_gather = 2;
set local work_mem = '128kB';
+set local hash_mem_multiplier = 1.0;
set local enable_parallel_hash = off;
explain (costs off)
select count(*) from simple r join simple s using (id);
@@ -172,6 +177,7 @@ rollback to settings;
savepoint settings;
set local max_parallel_workers_per_gather = 2;
set local work_mem = '192kB';
+set local hash_mem_multiplier = 1.0;
set local enable_parallel_hash = on;
explain (costs off)
select count(*) from simple r join simple s using (id);
@@ -192,6 +198,7 @@ rollback to settings;
savepoint settings;
set local max_parallel_workers_per_gather = 0;
set local work_mem = '128kB';
+set local hash_mem_multiplier = 1.0;
explain (costs off)
select count(*) FROM simple r JOIN bigger_than_it_looks s USING (id);
select count(*) FROM simple r JOIN bigger_than_it_looks s USING (id);
@@ -206,6 +213,7 @@ rollback to settings;
savepoint settings;
set local max_parallel_workers_per_gather = 2;
set local work_mem = '128kB';
+set local hash_mem_multiplier = 1.0;
set local enable_parallel_hash = off;
explain (costs off)
select count(*) from simple r join bigger_than_it_looks s using (id);
@@ -221,6 +229,7 @@ rollback to settings;
savepoint settings;
set local max_parallel_workers_per_gather = 1;
set local work_mem = '192kB';
+set local hash_mem_multiplier = 1.0;
set local enable_parallel_hash = on;
explain (costs off)
select count(*) from simple r join bigger_than_it_looks s using (id);
@@ -242,6 +251,7 @@ rollback to settings;
savepoint settings;
set local max_parallel_workers_per_gather = 0;
set local work_mem = '128kB';
+set local hash_mem_multiplier = 1.0;
explain (costs off)
select count(*) from simple r join extremely_skewed s using (id);
select count(*) from simple r join extremely_skewed s using (id);
@@ -255,6 +265,7 @@ rollback to settings;
savepoint settings;
set local max_parallel_workers_per_gather = 2;
set local work_mem = '128kB';
+set local hash_mem_multiplier = 1.0;
set local enable_parallel_hash = off;
explain (costs off)
select count(*) from simple r join extremely_skewed s using (id);
@@ -269,6 +280,7 @@ rollback to settings;
savepoint settings;
set local max_parallel_workers_per_gather = 1;
set local work_mem = '128kB';
+set local hash_mem_multiplier = 1.0;
set local enable_parallel_hash = on;
explain (costs off)
select count(*) from simple r join extremely_skewed s using (id);
@@ -285,6 +297,7 @@ rollback to settings;
savepoint settings;
set local max_parallel_workers_per_gather = 2;
set local work_mem = '4MB';
+set local hash_mem_multiplier = 1.0;
set local parallel_leader_participation = off;
select * from hash_join_batches(
$$
@@ -311,6 +324,7 @@ set max_parallel_workers_per_gather = 2;
set enable_material = off;
set enable_mergejoin = off;
set work_mem = '64kB';
+set hash_mem_multiplier = 1.0;
explain (costs off)
select count(*) from join_foo
left join (select b1.id, b1.t from join_bar b1 join join_bar b2 using (id)) ss
@@ -338,6 +352,7 @@ set max_parallel_workers_per_gather = 2;
set enable_material = off;
set enable_mergejoin = off;
set work_mem = '4MB';
+set hash_mem_multiplier = 1.0;
explain (costs off)
select count(*) from join_foo
left join (select b1.id, b1.t from join_bar b1 join join_bar b2 using (id)) ss
@@ -365,6 +380,7 @@ set max_parallel_workers_per_gather = 2;
set enable_material = off;
set enable_mergejoin = off;
set work_mem = '64kB';
+set hash_mem_multiplier = 1.0;
explain (costs off)
select count(*) from join_foo
left join (select b1.id, b1.t from join_bar b1 join join_bar b2 using (id)) ss
@@ -392,6 +408,7 @@ set max_parallel_workers_per_gather = 2;
set enable_material = off;
set enable_mergejoin = off;
set work_mem = '4MB';
+set hash_mem_multiplier = 1.0;
explain (costs off)
select count(*) from join_foo
left join (select b1.id, b1.t from join_bar b1 join join_bar b2 using (id)) ss
@@ -454,6 +471,7 @@ savepoint settings;
set max_parallel_workers_per_gather = 2;
set enable_parallel_hash = on;
set work_mem = '128kB';
+set hash_mem_multiplier = 1.0;
explain (costs off)
select length(max(s.t))
from wide left join (select id, coalesce(t, '') || '' as t from wide) s using (id);
diff --git a/src/test/regress/sql/memoize.sql b/src/test/regress/sql/memoize.sql
index c6ed5a2aa6..0979bcdf76 100644
--- a/src/test/regress/sql/memoize.sql
+++ b/src/test/regress/sql/memoize.sql
@@ -55,8 +55,9 @@ SELECT COUNT(*),AVG(t2.unique1) FROM tenk1 t1,
LATERAL (SELECT t2.unique1 FROM tenk1 t2 WHERE t1.twenty = t2.unique1) t2
WHERE t1.unique1 < 1000;
--- Reduce work_mem so that we see some cache evictions
+-- Reduce work_mem and hash_mem_multiplier so that we see some cache evictions
SET work_mem TO '64kB';
+SET hash_mem_multiplier TO 1.0;
SET enable_mergejoin TO off;
-- Ensure we get some evictions. We're unable to validate the hits and misses
-- here as the number of entries that fit in the cache at once will vary
@@ -126,6 +127,7 @@ WHERE unique1 < 3
RESET enable_seqscan;
RESET enable_mergejoin;
RESET work_mem;
+RESET hash_mem_multiplier;
RESET enable_bitmapscan;
RESET enable_hashjoin;