Message-ID: <f82fc7fbb69a8c8000ad74ced50381257fe57838.camel@cybertec.at>
Subject: Re: Disabling vacuum truncate for autovacuum
From: Laurenz Albe <laurenz.albe@cybertec.at>
To: Gurjeet Singh <gurjeet@singh.im>, Postgres Hackers
	 <pgsql-hackers@postgresql.org>
Cc: Will Storey <will@summercat.com>
Date: Mon, 27 Jan 2025 10:55:34 +0100
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On Thu, 2025-01-23 at 22:33 -0800, Gurjeet Singh wrote:
> > > I am also wondering if having an autovacuum setting to control it wou=
ld be
> > > a good idea for a feature.
> >=20
> > I'm all for that.
>=20
> Please see attached an initial patch to disable truncation behaviour in
> autovacuum. This patch retains the default behavior of autovacuum truncat=
ing
> relations. The user is allowed to change the behaviour and disable relati=
on
> truncations system-wide by setting autovacuum_disable_vacuum_truncate =3D=
 true.
> Better parameter names welcome :-)

I hope it is possible to override the global setting with the "vacuum_trunc=
ate"
option on an individual table.

My suggestion for the parameter name is "autovacuum_disable_truncate".

> One additional improvement I can think of is to emit a WARNING or NOTICE =
message
> that truncate operation is being skipped, perhaps only if the truncation
> would've freed up space over a certain threshold.

Interesting idea, but I think it is independent from this patch.

> Perhaps there's value in letting this parameter be specified at database =
level,
> but I'm not able to think of a reason why someone would want to disable t=
his
> behaviour on just one database. So leaving the parameter context to be th=
e same
> as most other autovacuum parameters: SIGHUP.

I can imagine setting that on only a certain database.  Different databases
typically have different applications, which have different needs.

Eventually, the patch should have documentation and regression tests.

Yours,
Laurenz Albe