From: "Hayato Kuroda (Fujitsu)" <kuroda.hayato@fujitsu.com>
To: 'Bertrand Drouvot' <bertranddrouvot.pg@gmail.com>
CC: Alexander Lakhin <exclusion@gmail.com>, "xunengzhou@gmail.com"
	<xunengzhou@gmail.com>, pgsql-hackers <pgsql-hackers@postgresql.org>
Subject: RE: t/035_standby_logical_decoding.pl might fail on attempt to read
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Thread-Topic: t/035_standby_logical_decoding.pl might fail on attempt to read
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Thread-Index: AQHc9ZLlUhM2VPCUS0qgMKq58+utYrYxXhiAgAKitgCAAFsCAIABZGsAgAAM1DA=
Date: Tue, 9 Jun 2026 07:05:20 +0000
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Precedence: bulk

Dear Bertrand,

Thanks for re-posting. Let's focus on the logical decoding stuff.

> > 0004: Add a test for 0003

I found a comment for the test.

```
+# Issue SQL decoding (read_local_xlog_page_guts path) on the pre-connected
+# session.
+$decode_session->query_until(
+       qr/decoding_started/, qq(
+       \\echo decoding_started
+       SELECT count(*) FROM pg_logical_slot_peek_changes('race_slot_sql', =
NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '1');
+));
```

Not sure, pg_logical_slot_peek_changes() can be finished without waiting an=
ything,
right? So why do we use query_until() and check the output here?
IIUC, the command can immediately raise an ERROR if the race happened. So i=
sn't it
enough to use safe_psql() to ensure the SQL function can work?

Best regards,
Hayato Kuroda
FUJITSU LIMITED