Feedback-ID: i0fe9450f:Fastmail
Date: Tue, 30 Sep 2025 16:37:25 +0900
From: Michael Paquier <michael@paquier.xyz>
To: Bertrand Drouvot <bertranddrouvot.pg@gmail.com>
Cc: Andres Freund <andres@anarazel.de>, pgsql-hackers@lists.postgresql.org
Subject: Re: [BUG]: the walsender does not update its IO statistics until it
 exits
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On Tue, Sep 30, 2025 at 07:14:14AM +0000, Bertrand Drouvot wrote:
> On Thu, Feb 27, 2025 at 12:09:46PM +0900, Michael Paquier wrote:
>> Agreed that something in the lines of non-transaction update of the
>> entries could be adapted in some cases, so +1 for the idea.  I suspect
>> that there would be cases where a single stats kind should be able to
>> handle both transactional and non-transactional flush cases.
>> Splitting that across two stats kinds would lead to a lot of
>> duplication.
>=20
> One option could be to use 2 pending lists for the variables stats and 2 =
flush
> callbacks for fixed stats. Thoughts?

Hmm.  I would have thought first about one pending area, and two
callbacks for the variable-sized stats, called with a different
timing because the stats to be flushed are the same aren't they?  For
example, if we are in a long analytical query, we would flush the IO
stats periodically, reset the pending data, repeat/rinse periodically,=20
and do a last round when we are done with the query in postgres.c.

Do we really need a second callback by the way?  It could be as well
the same flush callback, with an option to mark stats kinds that allow
a periodic flush.  The trick is knowing where the new reports calls
should happen.  The executor is the primary target area.

Or perhaps you think that the pending data of a stats kind could be
different if a kind allows transactional and non-transactional
flushes?=20
--
Michael

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