Horton

Re: relfilenode statistics

Kirill Reshke <reshkekirill@gmail.com>

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From: Kirill Reshke <reshkekirill@gmail.com>
To: Bertrand Drouvot <bertranddrouvot.pg@gmail.com>
Cc: Robert Haas <robertmhaas@gmail.com>, Michael Paquier <michael@paquier.xyz>, pgsql-hackers@lists.postgresql.org
Date: 2025-03-13T09:00:52Z
Lists: pgsql-hackers

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  1. Add more tests for relation statistics with rewrites

On Fri, 3 Jan 2025 at 21:18, Bertrand Drouvot
<bertranddrouvot.pg@gmail.com> wrote:

> As mentioned by Andres in [1], relying on the relation OID would not work to
> "recover" the stats because we don't have access to the relation oid during crash
> recovery. So, I'm going to resume working on the "initial" idea (i.e having the
> stats keyed by relfilenode).
>
> [1]: https://www.postgresql.org/message-id/xvetwjsnkhx2gp6np225g2h64f4mfmg6oopkuaiivrpzd2futj%40pflk55su36ho
>

Hmm. While it is true that catalog lookups cannot be performed during
crash recovery, is it really necessary to save and retrieve statistics
after a crash? Given that statistics are permitted to be outdated and
server crashes are anticipated to be infrequent, it looks loke losing
a few analysis runs due to server crashes is acceptable.
In any case, I am totally OK with the relfilenode-based method because
it is generally less restricted (to other postgresql parts e.g. wal-
replay ) and simpler.

Also, this patch needs a rebase;)



-- 
Best regards,
Kirill Reshke