Hello David,
23.01.2023 07:37, David Rowley wrote:
I've now pushed this.
I've discovered that the test query:
-- Ensure parallel aggregation is actually being used.
explain (costs off) select * from v_pagg_test order by y;
added by 16fd03e95 fails sometimes. For instance:
https://buildfarm.postgresql.org/cgi-bin/show_log.pl?nm=urutu&dt=2024-03-19%2021%3A04%3A05
--- /home/bf/bf-build/urutu/HEAD/pgsql/src/test/regress/expected/aggregates.out
2024-02-24 06:42:47.039073180 +0000
+++
/home/bf/bf-build/urutu/HEAD/pgsql.build/src/test/regress/results/aggregates.out
2024-03-19 22:24:18.155876135 +0000
@@ -1993,14 +1993,16 @@
Sort Key: pagg_test.y, (((unnest(regexp_split_to_array((string_agg((pagg_test.x)::text, ','::text)),
','::text))))::integer)
-> Result
-> ProjectSet
- -> Finalize HashAggregate
+ -> Finalize GroupAggregate
...
https://buildfarm.postgresql.org/cgi-bin/show_log.pl?nm=phycodurus&dt=2024-02-28%2007%3A38%3A27
https://buildfarm.postgresql.org/cgi-bin/show_log.pl?nm=avocet&dt=2024-02-08%2008%3A47%3A45
I suspect that these failures caused by autovacuum.
I could reproduce this plan change when running multiple tests in
parallel, and also with the attached test patch applied (several sleeps are
needed for autovacuum/relation_needs_vacanalyze() to get a non-zero
mod_since_analyze value from pgstat):
TEMP_CONFIG=/tmp/temp.config TESTS="test_setup create_index create_aggregate
aggregates" make -s check-tests
where /tmp/temp.config is:
autovacuum_naptime = 1
log_autovacuum_min_duration = 0
log_min_messages = INFO
log_min_error_statement = log
log_statement = 'all'
With EXPLAIN (VERBOSE), I see a slight change of the Seq Scan cost/rows
estimate:
... -> Parallel Seq Scan on public.pagg_test (cost=0.00..48.99 rows=2599
width=8)
vs
.. -> Parallel Seq Scan on public.pagg_test (cost=0.00..48.00 rows=2500
width=8)
(after automatic analyze of table "regression.public.pagg_test")
Best regards,
Alexander
diff --git a/src/test/regress/expected/aggregates.out b/src/test/regress/expected/aggregates.out
index d54a255e58..3de98c916d 100644
--- a/src/test/regress/expected/aggregates.out
+++ b/src/test/regress/expected/aggregates.out
@@ -1931,6 +1931,12 @@ select string_agg(v, decode('ee', 'hex')) from bytea_test_table;
drop table bytea_test_table;
-- Test parallel string_agg and array_agg
create table pagg_test (x int, y int);
+select pg_sleep(3);
+ pg_sleep
+----------
+
+(1 row)
+
insert into pagg_test
select (case x % 4 when 1 then null else x end), x % 10
from generate_series(1,5000) x;
@@ -1967,6 +1973,12 @@ from (
) a1
) a2
group by y;
+select pg_sleep(3);
+ pg_sleep
+----------
+
+(1 row)
+
-- Ensure results are correct.
select * from v_pagg_test order by y;
y | tmin | tmax | tndistinct | bmin | bmax | bndistinct | amin | amax | andistinct | aamin | aamax | aandistinct
@@ -1983,6 +1995,12 @@ select * from v_pagg_test order by y;
9 | 19 | 4999 | 250 | 1019 | 999 | 250 | 19 | 4999 | 250 | 19 | 4999 | 250
(10 rows)
+select pg_sleep(3);
+ pg_sleep
+----------
+
+(1 row)
+
-- Ensure parallel aggregation is actually being used.
explain (costs off) select * from v_pagg_test order by y;
QUERY PLAN
diff --git a/src/test/regress/sql/aggregates.sql b/src/test/regress/sql/aggregates.sql
index 441e01d150..25dd90ec65 100644
--- a/src/test/regress/sql/aggregates.sql
+++ b/src/test/regress/sql/aggregates.sql
@@ -750,6 +750,7 @@ drop table bytea_test_table;
-- Test parallel string_agg and array_agg
create table pagg_test (x int, y int);
+select pg_sleep(3);
insert into pagg_test
select (case x % 4 when 1 then null else x end), x % 10
from generate_series(1,5000) x;
@@ -789,9 +790,11 @@ from (
) a2
group by y;
+select pg_sleep(3);
-- Ensure results are correct.
select * from v_pagg_test order by y;
+select pg_sleep(3);
-- Ensure parallel aggregation is actually being used.
explain (costs off) select * from v_pagg_test order by y;
