Horton

Re: vacuum freeze - possible improvements

David Rowley <dgrowleyml@gmail.com>

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From: David Rowley <dgrowleyml@gmail.com>
To: Virender Singla <virender.cse@gmail.com>
Cc: Masahiko Sawada <sawada.mshk@gmail.com>, PostgreSQL-development <pgsql-hackers@postgresql.org>
Date: 2021-04-13T11:05:26Z
Lists: pgsql-hackers

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  1. Add wraparound failsafe to VACUUM.

On Tue, 13 Apr 2021 at 19:48, Virender Singla <virender.cse@gmail.com> wrote:
> Yes another thing here is anti wraparound vacuum also cleans dead tuples but i am not sure what we can do to avoid that.
> There can be vacuum to only freeze the tulpes?

You might want to have a look at [1], which was just pushed for PG14.

In particular:

> When the failsafe triggers, VACUUM takes extraordinary measures to
> finish as quickly as possible so that relfrozenxid and/or relminmxid can
> be advanced.  VACUUM will stop applying any cost-based delay that may be
> in effect.  VACUUM will also bypass any further index vacuuming and heap
> vacuuming -- it only completes whatever remaining pruning and freezing
> is required.  Bypassing index/heap vacuuming is enabled by commit
> 8523492d, which made it possible to dynamically trigger the mechanism
> already used within VACUUM when it is run with INDEX_CLEANUP off.

David

[1] https://git.postgresql.org/gitweb/?p=postgresql.git;a=commit;h=1e55e7d1755cefbb44982fbacc7da461fa8684e6