From: | "Drouvot, Bertrand" <bertranddrouvot(dot)pg(at)gmail(dot)com> |
---|---|
To: | Michael Paquier <michael(at)paquier(dot)xyz>, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
Cc: | Andres Freund <andres(at)anarazel(dot)de>, Magnus Hagander <magnus(at)hagander(dot)net>, Julien Rouhaud <rjuju123(at)gmail(dot)com>, David Steele <david(at)pgmasters(dot)net>, Tomas Vondra <tomas(dot)vondra(at)2ndquadrant(dot)com>, Robert Haas <robertmhaas(at)gmail(dot)com>, PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org> |
Subject: | Re: Checksum errors in pg_stat_database |
Date: | 2022-12-12 07:15:37 |
Message-ID: | b636dfec-d34e-2a33-52ab-40461bd5e312@gmail.com |
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Lists: | pgsql-hackers |
On 12/12/22 5:09 AM, Michael Paquier wrote:
> On Sun, Dec 11, 2022 at 08:48:15PM -0500, Tom Lane wrote:
>> I think a stats table indexed solely by relfilenode wouldn't be a great
>> idea, because you'd lose all the stats about a table as soon as you
>> do vacuum full/cluster/rewriting-alter-table/etc. Can we create two
>> index structures over the same stats table entries, so you can look
>> up by either relfilenode or OID? I'm not quite sure how to manage
>> rewrites, where you transiently have two relfilenodes for "the
>> same" table ... maybe we could allow multiple pointers to the same
>> stats entry??
>
> FWIW, I am not sure that I would care much if we were to dropped the
> stats associated to a relfilenode on a rewrite. In terms of checksum
> failures, tuples are deformed so if there is one checksum failure a
> rewrite would just not happen. The potential complexity is not really
> appealing compared to the implementation simplicity and its gains, and
> rewrites are lock-heavy so I'd like to think that people avoid them
> (cough)..
Agree that this is less "problematic" for the checksum use case.
On the other hand, losing IO stats (as the ones we could add later on, suggested by Andres up-thread) looks more of a concern to me.
Regards,
--
Bertrand Drouvot
PostgreSQL Contributors Team
RDS Open Source Databases
Amazon Web Services: https://aws.amazon.com
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