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From: Amit Kapila <amit.kapila16@gmail.com>
Date: Mon, 20 Apr 2026 11:34:17 +0530
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 <CAA4eK1+Y7qwvzSjeY=KWWLHw3wQNxD7ebr5FoWTuBOYpRGhc3A@mail.gmail.com>
Subject: Re: Possible premature SNAPBUILD_CONSISTENT with DB-specific
 running_xacts
To: SATYANARAYANA NARLAPURAM <satyanarlapuram@gmail.com>
Cc: PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>,
	=?UTF-8?Q?=C3=81lvaro_Herrera?= <alvherre@kurilemu.de>,
	Antonin Houska <ah@cybertec.at>
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On Mon, Apr 20, 2026 at 12:29=E2=80=AFAM SATYANARAYANA NARLAPURAM
<satyanarlapuram@gmail.com> wrote:
>
> A cluster-wide decoder must never have its snapshot-builder state changed
> by a database-specific running_xacts record. Adding a check to return it =
early.
> I think otherwise a cluster wide decoder can potentially go to
> SNAPSHOT_CONSISTENT state immediately even though transactions older
> than nextXid are still in progress on a different DB (not tracked by runn=
ing_xact
> record). This race is now possible with cluster wide decoders and Repack
> concurrently run.
>

I think this has been discussed previously, see [1]. As per my
understanding, we are not in agreement for the need of this
db-specific handling in the snapbuilder, see [2][3]. So, adding more
improvements/fixes on top of it doesn't sound advisable.

[1] - https://www.postgresql.org/message-id/CAA4eK1KWDbBk4FgbbWdivQLrPPzR4z=
gvfnHK4WjWC78rbuRVbg%40mail.gmail.com
[2] - https://www.postgresql.org/message-id/cdgw4sbbfcgk6du3iv54r2dgiy4tfyw=
oklbotlmj4irxavdcr3%40glxfw5jj277q
[3] - https://www.postgresql.org/message-id/pveffyxhnuurhb44uzqlwo3rkyzorkf=
h2rot7uwzlf2axhfvbp%407nrs2omysxkc

--=20
With Regards,
Amit Kapila.