MIME-Version: 1.0
References: 
 <CACG=ezaWg7_nt-8ey4aKv2w9LcuLthHknwCawmBgEeTnJrJTcw@mail.gmail.com>
 <4535f3aa-3220-4760-b1f5-2bc91f248e03@iki.fi>
 <CACG=ezbKwypBp=14q9+hMQApus3=1hKxJ9x1+KinUhtT48570Q@mail.gmail.com>
 <2bc58592-9d74-4af0-bdd1-1a88e8683f7c@iki.fi>
 <CACG=ezZwdvsijzuXE3hex3xHcoz75EQYBXRTsQJVwbo5J5sS3g@mail.gmail.com>
 <CACG=ezbs912S58=uR17b4w8uuWv1=OcCRaTW_OWdFm4+tXZA6w@mail.gmail.com>
 <CAGjGUA+BfcWyccNN4=tHsW_E-koRxbg8h8ut6hjvPsHMgmek6w@mail.gmail.com>
 <CACG=ezYbYO_KHWdeDedbDcY0tOS0JfaqBxG3=bG5+DdsDK4MpQ@mail.gmail.com>
 <CACG=ezYpZRPwoRCz_h3Qerd3XJNdpTHCpwGbZphNdy26tA4_qQ@mail.gmail.com>
 <36531c0e-292c-409d-bbc7-a252cf6e910a@iki.fi>
 <54aa8f65-f0e4-4464-b543-e0399c1cab1e@iki.fi>
 <CACG=ezYUJSvnuxntkURNWo_1vZ+AtmcQfqd_h6WgDzGaudfw+Q@mail.gmail.com>
 <4a9dda70-0af7-41a4-9636-b168f2fc48ef@iki.fi>
 <46cc45e9-fddd-44bc-bcb3-96889aafd921@iki.fi>
 <CAExHW5tUEkiQrvm9hgccjKUNkWBnJ5_HDUrAwiHBTxu+Vuj29Q@mail.gmail.com>
 <6c298bc4-7029-4c1d-bf16-3e094842ce32@iki.fi>
 <9ee6324a-44fc-42fb-bf8e-7c3b53395588@iki.fi>
In-Reply-To: <9ee6324a-44fc-42fb-bf8e-7c3b53395588@iki.fi>
From: Alexander Korotkov <aekorotkov@gmail.com>
Date: Tue, 2 Dec 2025 16:11:34 +0200
Message-ID: 
 <CAPpHfdsMd9TQ8ZbMnStMfFvBoBMwBCSC+8zcOYY9VDMYQzUYyQ@mail.gmail.com>
Subject: Re: POC: make mxidoff 64 bits
To: Heikki Linnakangas <hlinnaka@iki.fi>
Cc: Maxim Orlov <orlovmg@gmail.com>, Alvaro Herrera <alvherre@alvh.no-ip.org>,
	wenhui qiu <qiuwenhuifx@gmail.com>,
	Postgres hackers <pgsql-hackers@lists.postgresql.org>,
	Ashutosh Bapat <ashutosh.bapat.oss@gmail.com>
Content-Type: text/plain; charset="UTF-8"
Content-Transfer-Encoding: quoted-printable
Archived-At: 
 <https://www.postgresql.org/message-id/CAPpHfdsMd9TQ8ZbMnStMfFvBoBMwBCSC%2B8zcOYY9VDMYQzUYyQ%40mail.gmail.com>
Precedence: bulk

Hi, Heikki!

On Tue, Nov 25, 2025 at 12:07=E2=80=AFPM Heikki Linnakangas <hlinnaka@iki.f=
i> wrote:
> Looking at the upgrade code, in light of the "IPC/MultixactCreation on
> the Standby server" thread [1], I think we need to make it more
> tolerant. It's possible that there are 0 offsets in
> pg_multixact/offsets. That might or might not be a problem: it's OK as
> long as those multixids don't appear in any heap table, or you might
> actually have lost those multixids, which is bad but the damage has
> already been done and upgrade should not get stuck on it.
> GetOldMultiXactIdSingleMember() currently asserts that the offset is
> never zero, but it should try to do something sensible in that case
> instead of just failing.

Thank you for your work on this subject.  It's very much appreciated.

I'd like to raise the question about compression again.  You have
fairly criticized non-deterministic compression, but what do you think
about deterministic one that I've proposed [1].  I understand that
multixact offsets are subject of growth and their limit is not
removed.  However, it's still several extra gigabytes for multixact
offsets, which we could save.

Links.
1. https://www.postgresql.org/message-id/CAPpHfduDFLXATvBkUiOjyvZUBZXhK_pj5=
zjVpxvrJzkRVq%2B8Lw%40mail.gmail.com

------
Regards,
Alexander Korotkov
Supabase