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help / color / mirror / Atom feedFrom: Michael Paquier <[email protected]>
To: Andres Freund <[email protected]>
Cc: Postgres hackers <[email protected]>
Cc: [email protected]
Subject: Re: WAL-logging facility for pgstats kinds
Date: Thu, 9 Jan 2025 13:53:48 +0900
Message-ID: <[email protected]> (raw)
In-Reply-To: <xvetwjsnkhx2gp6np225g2h64f4mfmg6oopkuaiivrpzd2futj@pflk55su36ho>
References: <[email protected]>
<xvetwjsnkhx2gp6np225g2h64f4mfmg6oopkuaiivrpzd2futj@pflk55su36ho>
On Thu, Jan 02, 2025 at 08:08:42PM -0500, Andres Freund wrote:
> I can't think of a real case where we would want to WAL log the stats
> themselves, rather than re-emitting stats during replay based on the WAL
> record of the "underlying object".
>
> Do you have counter-examples?
I'm not sure if the rebuild based on the WAL records is simpler than
logging a snapshot of them that the startup process could digest.
Anyway, I've also wanted to be able to replicate stats for historical
tracking for stats logged through hooks, and a second case was
injection point stats. All these would require registering a custom
rmgr on top of a custom stats kind, and centralizing the logic eases a
lot some of the sanity checks they'd require as the redo callback of a
stats kind can just be attached to its PgStat_KindInfo.
I know that Lucas has been playing a bit with the area, and perhaps
he has more cases in mind where the replication of stats data could be
relevant. So I am adding him in CC. Perhaps I could be wrong, of
course.
--
Michael
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