public inbox for [email protected]
help / color / mirror / Atom feedFrom: Antonin Houska <[email protected]>
To: Alvaro Herrera <[email protected]>
Cc: Matthias van de Meent <[email protected]>
Cc: Mihail Nikalayeu <[email protected]>
Cc: Pg Hackers <[email protected]>
Cc: Robert Treat <[email protected]>
Subject: Re: Adding REPACK [concurrently]
Date: Tue, 17 Mar 2026 20:57:06 +0100
Message-ID: <91049.1773777426@localhost> (raw)
In-Reply-To: <9548.1773744820@localhost>
References: <[email protected]>
<9548.1773744820@localhost>
Antonin Houska <[email protected]> wrote:
> Alvaro Herrera <[email protected]> wrote:
>
> > On 2026-Mar-16, Matthias van de Meent wrote:
> >
> > > On Mon, 16 Mar 2026 at 21:15, Antonin Houska <[email protected]> wrote:
> >
> > > > Anyway (fortunately?), the concurrent use of slots by REPACK is limited
> > > > because, during the initialization of logical decoding, the backend needs to
> > > > wait for all the transactions having XID assigned to finish, and these include
> > > > the already running REPACK commands. See SnapBuildWaitSnapshot() and callers
> > > > if you're interested in details.
> > >
> > > Huh, so would you be able to run more than one Repack Concurrently in
> > > the same database? ISTM that would not be possible, apart from
> > > possibly a mechanism comparable to the SAFE_IN_IC flag (to not wait on
> > > those backends).
> >
> > Yeah, this sounds kind of bad news ...
>
> Admittedly, it is a problem. I tried to address this in pg_squeeze by
> pre-allocating slots when it's clear (due to scheduling) that more than one
> table needs to be processed. This was an effort to achieve the best possible
> performance rather than a response to complaints of users about low
> throughput. Nevertheless, I'm glad I happened to mention it before it's too
> late.
>
> Regarding solution, a flag like SAFE_IN_IC alone does not help. The
> information that particular transaction is used by REPACK (and therefore it
> does not have to be decoded) would need to be propagated to the
> xl_running_xacts WAL record too.
0007 in the next version tries to implement that.
--
Antonin Houska
Web: https://www.cybertec-postgresql.com
view thread (19+ messages) latest in thread
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]
Subject: Re: Adding REPACK [concurrently]
In-Reply-To: <91049.1773777426@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