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Fix flakey pg_stat_io test

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Wrap test of pg_stat_io's tracking of shared buffer reads in a transaction to
prevent concurrent accesses (e.g. by autovacuum) causing spurious test
failures.

Reported-by: Tom Lane <tgl@sss.pgh.pa.us>
Author: Melanie Plageman <melanieplageman@gmail.com>
Discussion: https://www.postgresql.org/message-id/20230306190919.ai6mxdq3sygyyths%40awork3.anarazel.de
This commit is contained in:
Andres Freund
2023-03-07 10:03:42 -08:00
parent e20b1ea157
commit 1be0fdb9de
2 changed files with 8 additions and 0 deletions
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4
src/test/regress/expected/stats.out
View File

@ -1181,6 +1181,9 @@ SELECT current_setting('fsync') = 'off'
-- from it to cause it to be read back into shared buffers.
SELECT sum(reads) AS io_sum_shared_before_reads
FROM pg_stat_io WHERE io_context = 'normal' AND io_object = 'relation' \gset
-- Do this in a transaction to prevent spurious failures due to concurrent accesses to our newly
-- rewritten table, e.g. by autovacuum.
BEGIN;
ALTER TABLE test_io_shared SET TABLESPACE regress_tblspace;
-- SELECT from the table so that the data is read into shared buffers and
-- io_context 'normal', io_object 'relation' reads are counted.
@ -1190,6 +1193,7 @@ SELECT COUNT(*) FROM test_io_shared;
100
(1 row)
COMMIT;
SELECT pg_stat_force_next_flush();
pg_stat_force_next_flush
--------------------------

4
src/test/regress/sql/stats.sql
View File

@ -576,10 +576,14 @@ SELECT current_setting('fsync') = 'off'
-- from it to cause it to be read back into shared buffers.
SELECT sum(reads) AS io_sum_shared_before_reads
FROM pg_stat_io WHERE io_context = 'normal' AND io_object = 'relation' \gset
-- Do this in a transaction to prevent spurious failures due to concurrent accesses to our newly
-- rewritten table, e.g. by autovacuum.
BEGIN;
ALTER TABLE test_io_shared SET TABLESPACE regress_tblspace;
-- SELECT from the table so that the data is read into shared buffers and
-- io_context 'normal', io_object 'relation' reads are counted.
SELECT COUNT(*) FROM test_io_shared;
COMMIT;
SELECT pg_stat_force_next_flush();
SELECT sum(reads) AS io_sum_shared_after_reads
FROM pg_stat_io WHERE io_context = 'normal' AND io_object = 'relation' \gset