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From: Antonin Houska <[email protected]>
To: Alvaro Herrera <[email protected]>
Cc: Michael Banck <[email protected]>
Cc: Junwang Zhao <[email protected]>
Cc: Kirill Reshke <[email protected]>
Cc: Pavel Stehule <[email protected]>
Cc: Michael Paquier <[email protected]>
Cc: PostgreSQL Hackers <[email protected]>
Subject: Re: why there is not VACUUM FULL CONCURRENTLY?
Date: Fri, 31 Jan 2025 07:27:50 +0100
Message-ID: <10749.1738304870@antos> (raw)
In-Reply-To: <[email protected]>
References: <[email protected]>

Alvaro Herrera <[email protected]> wrote:

> On 2025-Jan-30, Michael Banck wrote:
> 
> > > I haven't addressed the problem of a new command yet - for that I'd like to
> > > see some sort of consensus, so that I do not have to do all the related
> > > changes many times.
> > 
> > Well, looks like this patch-set is blocked on the bikeshedding part?
> > 
> > Somebody should call a shot here, then.
> 
> A bunch of people discussed this patch in today's developer meeting in
> Brussels.  There's pretty much a consensus on using the verb REPACK
> CONCURRENTLY for this new command -- where unadorned REPACK would be
> VACUUM FULL, and we'd have something like REPACK WITH INDEX or maybe
> REPACK USING INDEX to take the CLUSTER place.

Thanks for discussing the patch.

I assume the patch should mark CLUSTER deprecated rather than removing it
immediately.

> For the record, there was an observation that 1) if logical decoding is
> not enabled, REPACK CONCURRENTLY would not work, and 2) that sites being
> forced to enable logical decoding (even if transiently) to allow this,
> might take a considerable performance hit, and that we shouldn't
> entangle our features in that way.  I don't have an opinion on these
> things at this point; knowing more about exactly what the performance
> impact is would be good.  Regarding logical decoding, the conversation
> continued that maybe it'd be good if the feature can be automatically
> enabled transiently for that particular table for as long as needed, and
> disabled afterwards.  But like with the previous concern, I don't really
> have an opinion without understanding it more deeply.

Enabling the logical decoding transiently makes sense to me.

I also agree that tables not being REPACKed should be treated as not being
logically decoded, i.e. the logical decoding specific information should not
be written to WAL for them. Neither time nor energy should be wasted :-)

I'll try to implement these requirements the next version.

-- 
Antonin Houska
Web: https://www.cybertec-postgresql.com

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