From: Antonin Houska <ah@cybertec.at>
To: Alvaro Herrera <alvherre@alvh.no-ip.org>
cc: Michael Banck <mbanck@gmx.net>, Junwang Zhao <zhjwpku@gmail.com>,
    Kirill Reshke <reshkekirill@gmail.com>,
    Pavel Stehule <pavel.stehule@gmail.com>,
    Michael Paquier <michael@paquier.xyz>,
    PostgreSQL Hackers <pgsql-hackers@postgresql.org>
Subject: Re: why there is not VACUUM FULL CONCURRENTLY?
In-reply-to: <202501310932.ugw3k5c4orgv@alvherre.pgsql>
References: <202501310932.ugw3k5c4orgv@alvherre.pgsql>
Comments: In-reply-to Alvaro Herrera <alvherre@alvh.no-ip.org>
   message dated "Fri, 31 Jan 2025 10:32:00 +0100."
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Date: Fri, 31 Jan 2025 11:15:24 +0100
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Alvaro Herrera <alvherre@alvh.no-ip.org> wrote:

> On 2025-Jan-31, Antonin Houska wrote:
> 
> Something that Robert Haas just mentioned to me is handling of row
> locks: if concurrent transactions are keeping rows in the original table
> locked (especially SELECT FOR KEY SHARE, since that's not considered by
> logical decoding at present and it would be possible to break foreign
> keys if we just do nothing), them we need these to be "transferred" to
> the new table somehow.

The current implementation acquires AccessExclusiveLock on the table
(supposedly for very short time) so it can swap the table and index
files. Once we have that lock, I think the transactions holding the row locks
should no longer be running. Or can the row lock "survive" the table lock
somehow?

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