Hello!
On 30.03.2022 22:36, Robert Haas wrote:
I don't think that the idea of "extra" WAL records is very principled.
It's pretty vague what "extra" means, and your definition seems to be
basically "whatever would be needed to make this test case pass." I
think the problem is basically with the test cases's idea that # of
WAL records and # of table rows ought to be equal. I think that's just
false. In general, we'd also have to worry about index insertions,
which would provoke variable numbers of WAL records depending on
whether they cause a page split. And we'd have to worry about TOAST
table insertions, which could produce different numbers of records
depending on the size of the data, the configured block size and TOAST
threshold, and whether the TOAST table index incurs a page split.
Thank you very much for this information. I really didn't take it into
account.
If it's true that this test case sometimes randomly fails, then we
ought to fix that somehow, maybe by just removing this particular
check from the test case, or changing it to >=, or something like
that. But I don't think adding a new counter is the right idea.
Indeed. Then there is a very simple solution for this particular case as
wal_records counter may only sometime becomes greater but never less.
The corresponding patch is attached.
With best regards,
--
Anton A. Melnikov
Postgres Professional: http://www.postgrespro.com
The Russian Postgres Company
commit 742d16413ebfe4f556e0f676a3a8785b638d245a
Author: Anton A. Melnikov <a.melni...@postgrespro.ru>
Date: Thu Mar 31 18:00:07 2022 +0300
Fix possible fails in pg_stat_statements test via test rework.
diff --git a/contrib/pg_stat_statements/expected/pg_stat_statements.out b/contrib/pg_stat_statements/expected/pg_stat_statements.out
index e0abe34bb6..8706409739 100644
--- a/contrib/pg_stat_statements/expected/pg_stat_statements.out
+++ b/contrib/pg_stat_statements/expected/pg_stat_statements.out
@@ -234,18 +234,18 @@ SET pg_stat_statements.track_utility = FALSE;
SELECT query, calls, rows,
wal_bytes > 0 as wal_bytes_generated,
wal_records > 0 as wal_records_generated,
-wal_records = rows as wal_records_as_rows
+wal_records >= rows as wal_records_ge_rows
FROM pg_stat_statements ORDER BY query COLLATE "C";
- query | calls | rows | wal_bytes_generated | wal_records_generated | wal_records_as_rows
+ query | calls | rows | wal_bytes_generated | wal_records_generated | wal_records_ge_rows
-----------------------------------------------------------+-------+------+---------------------+-----------------------+---------------------
DELETE FROM pgss_test WHERE a > $1 | 1 | 1 | t | t | t
- DROP TABLE pgss_test | 1 | 0 | t | t | f
+ DROP TABLE pgss_test | 1 | 0 | t | t | t
INSERT INTO pgss_test VALUES(generate_series($1, $2), $3) | 1 | 10 | t | t | t
SELECT pg_stat_statements_reset() | 1 | 1 | f | f | f
SELECT query, calls, rows, +| 0 | 0 | f | f | t
wal_bytes > $1 as wal_bytes_generated, +| | | | |
wal_records > $2 as wal_records_generated, +| | | | |
- wal_records = rows as wal_records_as_rows +| | | | |
+ wal_records >= rows as wal_records_ge_rows +| | | | |
FROM pg_stat_statements ORDER BY query COLLATE "C" | | | | |
SET pg_stat_statements.track_utility = FALSE | 1 | 0 | f | f | t
UPDATE pgss_test SET b = $1 WHERE a > $2 | 1 | 3 | t | t | t
diff --git a/contrib/pg_stat_statements/sql/pg_stat_statements.sql b/contrib/pg_stat_statements/sql/pg_stat_statements.sql
index dffd2c8c18..a01f183727 100644
--- a/contrib/pg_stat_statements/sql/pg_stat_statements.sql
+++ b/contrib/pg_stat_statements/sql/pg_stat_statements.sql
@@ -122,7 +122,7 @@ SET pg_stat_statements.track_utility = FALSE;
SELECT query, calls, rows,
wal_bytes > 0 as wal_bytes_generated,
wal_records > 0 as wal_records_generated,
-wal_records = rows as wal_records_as_rows
+wal_records >= rows as wal_records_ge_rows
FROM pg_stat_statements ORDER BY query COLLATE "C";
--
