public inbox for [email protected]  

help / color / mirror / Atom feed

From: Antonin Houska <[email protected]>
To: Alvaro Herrera <[email protected]>
Cc: Marcos Pegoraro <[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, 04 Apr 2025 12:28:36 +0200
Message-ID: <13028.1743762516@localhost> (raw)
In-Reply-To: <[email protected]>
References: <[email protected]>

Alvaro Herrera <[email protected]> wrote:

> On 2025-Apr-01, Antonin Houska wrote:
> 
> > Besides that, it occurred to me that 0005 ("Preserve visibility
> > information of the concurrent data changes.") will probably introduce
> > significant overhead. The problem is that the table we're repacking is
> > treated like a catalog, for reorderbuffer.c to generate snapshots that
> > we need to replay UPDATE / DELETE commands on the new table.
> > 
> > contrib/test_decoding can be used to demonstrate the difference
> > between ordinary and catalog tables:
> > 
> > [.. ordinary ..]
> > Execution Time: 3521.190 ms
> > [.. catalog ..]
> > Execution Time: 6561.634 ms
> 
> Significant indeed.  Thinking about the scenarios in which I envision
> people using REPACK CONCURRENTLY (mostly, cases where very large tables
> have accumulated considerable amounts of bloat) and considering the size
> of the patch, I think the case for treating it as concurrent-safe is not
> credible, at least not at this stage -- not only because of this
> performance impact, but also because of the additional code complexity,
> which I'm really doubtful we can address at this stage.  I would suggest
> to put that patch aside for now, maybe with a doc warning that
> "repacking a table would cause visibility information to be lost"; and
> then address that aspect later on, after this feature has gone through
> some battle-hardening.

ok, I'll adjust the patch set.

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

view thread (2+ messages)

reply

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Reply to all the recipients using the --to and --cc options:
  reply via email

  To: [email protected]
  Cc: [email protected], [email protected], [email protected], [email protected], [email protected], [email protected], [email protected], [email protected]
  Subject: Re: why there is not VACUUM FULL CONCURRENTLY?
  In-Reply-To: <13028.1743762516@localhost>

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

This inbox is served by agora; see mirroring instructions
for how to clone and mirror all data and code used for this inbox