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CREATE INDEX: don't update table stats if autovacuum=off.

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We previously fixed this for binary upgrade in 71b66171d0, but a
similar problem remained when dumping statistics without data.

Fix by not opportunistically updating table stats during CREATE INDEX
when autovacuum is disabled. For stats to be stable at all, the server
needs to be aware that it should not take every opportunity to update
stats. Per discussion, autovacuum=off is a signal that the user
expects stats to be stable; though if necessary, we could create
a more specific mode in the future.

Reported-by: Ashutosh Bapat <ashutosh.bapat.oss@gmail.com>
Discussion: https://postgr.es/m/CAExHW5vf9D+8-a5_BEX3y=2y_xY9hiCxV1=C+FnxDvfprWvkng@mail.gmail.com
Discussion: https://postgr.es/m/ca81cbf6e6ea2af838df972801ad4da52640a503.camel%40j-davis.com
This commit is contained in:
Jeff Davis 2025-03-06 19:36:34 -08:00
parent 19e57f4f78
commit d611f8b158
3 changed files with 68 additions and 0 deletions
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22
src/backend/catalog/index.c
View File

@ -63,6 +63,7 @@
#include "optimizer/optimizer.h"
#include "parser/parser.h"
#include "pgstat.h"
#include "postmaster/autovacuum.h"
#include "rewrite/rewriteManip.h"
#include "storage/bufmgr.h"
#include "storage/lmgr.h"
@ -2840,6 +2841,27 @@ index_update_stats(Relation rel,
*/
update_stats = reltuples >= 0 && !IsBinaryUpgrade;
/*
* If autovacuum is off, user may not be expecting table relstats to
* change. This can be important when restoring a dump that includes
* statistics, as the table statistics may be restored before the index is
* created, and we want to preserve the restored table statistics.
*/
if (AutoVacuumingActive())
{
if (rel->rd_rel->relkind == RELKIND_RELATION ||
rel->rd_rel->relkind == RELKIND_TOASTVALUE ||
rel->rd_rel->relkind == RELKIND_MATVIEW)
{
StdRdOptions *options = (StdRdOptions *) rel->rd_options;
if (options != NULL && !options->autovacuum.enabled)
update_stats = false;
}
}
else
update_stats = false;
/*
* Finish I/O and visibility map buffer locks before
* systable_inplace_update_begin() locks the pg_class buffer. The rd_rel

29
src/test/regress/expected/stats_import.out
View File

@ -12,7 +12,36 @@ CREATE TABLE stats_import.test(
arange int4range,
tags text[]
) WITH (autovacuum_enabled = false);
SELECT
pg_catalog.pg_restore_relation_stats(
'relation', 'stats_import.test'::regclass,
'relpages', 18::integer,
'reltuples', 21::real,
'relallvisible', 24::integer,
'relallfrozen', 27::integer);
pg_restore_relation_stats
---------------------------
t
(1 row)
-- CREATE INDEX on a table with autovac disabled should not overwrite
-- stats
CREATE INDEX test_i ON stats_import.test(id);
SELECT relname, relpages, reltuples, relallvisible, relallfrozen
FROM pg_class
WHERE oid = 'stats_import.test'::regclass
ORDER BY relname;
relname | relpages | reltuples | relallvisible | relallfrozen
---------+----------+-----------+---------------+--------------
test | 18 | 21 | 24 | 27
(1 row)
SELECT pg_clear_relation_stats('stats_import.test'::regclass);
pg_clear_relation_stats
-------------------------
(1 row)
--
-- relstats tests
--

17
src/test/regress/sql/stats_import.sql
View File

@ -15,8 +15,25 @@ CREATE TABLE stats_import.test(
tags text[]
) WITH (autovacuum_enabled = false);
SELECT
pg_catalog.pg_restore_relation_stats(
'relation', 'stats_import.test'::regclass,
'relpages', 18::integer,
'reltuples', 21::real,
'relallvisible', 24::integer,
'relallfrozen', 27::integer);
-- CREATE INDEX on a table with autovac disabled should not overwrite
-- stats
CREATE INDEX test_i ON stats_import.test(id);
SELECT relname, relpages, reltuples, relallvisible, relallfrozen
FROM pg_class
WHERE oid = 'stats_import.test'::regclass
ORDER BY relname;
SELECT pg_clear_relation_stats('stats_import.test'::regclass);
--
-- relstats tests
--