Re: Changing the state of data checksums in a running cluster

From: Tomas Vondra <tomas(at)vondra(dot)me>
To: Michael Paquier <michael(at)paquier(dot)xyz>
Cc: Alexander Lakhin <exclusion(at)gmail(dot)com>, Daniel Gustafsson <daniel(at)yesql(dot)se>, Andres Freund <andres(at)anarazel(dot)de>, Heikki Linnakangas <hlinnaka(at)iki(dot)fi>, Bernd Helmle <mailings(at)oopsware(dot)de>, Michael Banck <mbanck(at)gmx(dot)net>, PostgreSQL Hackers <pgsql-hackers(at)lists(dot)postgresql(dot)org>
Subject: Re: Changing the state of data checksums in a running cluster
Date: 2026-08-24 09:38:07
Message-ID: 2bcd05e4-c98c-4b0e-a561-90e75a60206c@vondra.me
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On 8/24/26 03:25, Michael Paquier wrote:
> On Sun, Aug 23, 2026 at 07:30:32PM +0200, Tomas Vondra wrote:
>> I'm 99% sure this is a configuration issue in the test, not a bug in the
>> online checksums code. It happens because with
>>
>> debug_parallel_query = regress
>
> Is the coverage provided by debug_parallel_query useful to have in
> this context?
>
>> queries start enough parallel workers to exhaust max_worker_processes,
>> and so we fail to start the checksum worker.
>>
>> I've modified the TAP tests to add
>>
>> max_worker_processes = 16
>> max_parallel_workers = 16
>>
>> and with that change it passes just fine.
>
> One option would be debug_parallel_query = off to shave the number of
> workers spawned.

Yeah. I don't think "debug_parallel_query = regress" is not very helpful
or this test, 99% of the code is in the background worker anyway.

regards

--
Tomas Vondra

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