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Stabilize pg_stat_io writes test

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Counting writes only for io_context = 'normal' is unreliable, as backends
using a buffer access strategy could flush all of the dirty buffers out from
under the other backends and checkpointer. Change the test to count writes in
any context. This achieves roughly the same coverage anyway.

Reported-by: Justin Pryzby <pryzby@telsasoft.com>
Author: Melanie Plageman <melanieplageman@gmail.com>
Discussion: https://www.postgresql.org/message-id/ZAnWU8WbXEDjrfUE%40telsasoft.com
This commit is contained in:
Andres Freund 2023-03-20 18:16:06 -07:00
parent 7730ceb43f
commit ef719e7b32
2 changed files with 8 additions and 9 deletions
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8
src/test/regress/expected/stats.out
View File

@ -1137,6 +1137,9 @@ SELECT pg_stat_get_subscription_stats(NULL);
-- extends.
SELECT sum(extends) AS io_sum_shared_before_extends
FROM pg_stat_io WHERE io_context = 'normal' AND io_object = 'relation' \gset
SELECT sum(writes) AS writes, sum(fsyncs) AS fsyncs
FROM pg_stat_io
WHERE io_object = 'relation' \gset io_sum_shared_before_
CREATE TABLE test_io_shared(a int);
INSERT INTO test_io_shared SELECT i FROM generate_series(1,100)i;
SELECT pg_stat_force_next_flush();
@ -1155,15 +1158,12 @@ SELECT :io_sum_shared_after_extends > :io_sum_shared_before_extends;
-- After a checkpoint, there should be some additional IOCONTEXT_NORMAL writes
-- and fsyncs.
SELECT sum(writes) AS writes, sum(fsyncs) AS fsyncs
FROM pg_stat_io
WHERE io_context = 'normal' AND io_object = 'relation' \gset io_sum_shared_before_
-- See comment above for rationale for two explicit CHECKPOINTs.
CHECKPOINT;
CHECKPOINT;
SELECT sum(writes) AS writes, sum(fsyncs) AS fsyncs
FROM pg_stat_io
WHERE io_context = 'normal' AND io_object = 'relation' \gset io_sum_shared_after_
WHERE io_object = 'relation' \gset io_sum_shared_after_
SELECT :io_sum_shared_after_writes > :io_sum_shared_before_writes;
?column?
----------

9
src/test/regress/sql/stats.sql
View File

@ -549,6 +549,9 @@ SELECT pg_stat_get_subscription_stats(NULL);
-- extends.
SELECT sum(extends) AS io_sum_shared_before_extends
FROM pg_stat_io WHERE io_context = 'normal' AND io_object = 'relation' \gset
SELECT sum(writes) AS writes, sum(fsyncs) AS fsyncs
FROM pg_stat_io
WHERE io_object = 'relation' \gset io_sum_shared_before_
CREATE TABLE test_io_shared(a int);
INSERT INTO test_io_shared SELECT i FROM generate_series(1,100)i;
SELECT pg_stat_force_next_flush();
@ -558,16 +561,12 @@ SELECT :io_sum_shared_after_extends > :io_sum_shared_before_extends;
-- After a checkpoint, there should be some additional IOCONTEXT_NORMAL writes
-- and fsyncs.
SELECT sum(writes) AS writes, sum(fsyncs) AS fsyncs
FROM pg_stat_io
WHERE io_context = 'normal' AND io_object = 'relation' \gset io_sum_shared_before_
-- See comment above for rationale for two explicit CHECKPOINTs.
CHECKPOINT;
CHECKPOINT;
SELECT sum(writes) AS writes, sum(fsyncs) AS fsyncs
FROM pg_stat_io
WHERE io_context = 'normal' AND io_object = 'relation' \gset io_sum_shared_after_
WHERE io_object = 'relation' \gset io_sum_shared_after_
SELECT :io_sum_shared_after_writes > :io_sum_shared_before_writes;
SELECT current_setting('fsync') = 'off'
OR :io_sum_shared_after_fsyncs > :io_sum_shared_before_fsyncs;