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Re: Assertion failure in SnapBuildInitialSnapshot()

Amit Kapila <amit.kapila16@gmail.com>

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From: Amit Kapila <amit.kapila16@gmail.com>
To: Andres Freund <andres@anarazel.de>
Cc: Thomas Munro <thomas.munro@gmail.com>, PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>, Sawada Masahiko <sawada.mshk@gmail.com>, kuroda.hayato@fujitsu.com
Date: 2022-11-15T10:50:00Z
Lists: pgsql-hackers 
On Tue, Nov 15, 2022 at 8:08 AM Andres Freund <andres@anarazel.de> wrote:
>
> On 2022-11-14 17:25:31 -0800, Andres Freund wrote:
> > Hm, also, shouldn't the patch adding CRS_USE_SNAPSHOT have copied more of
> > SnapBuildExportSnapshot()? Why aren't the error checks for
> > SnapBuildExportSnapshot() needed? Why don't we need to set XactReadOnly? Which
> > transactions are we even in when we import the snapshot (cf.
> > SnapBuildExportSnapshot() doing a StartTransactionCommand()).
>
> Most of the checks for that are in CreateReplicationSlot() - but not al,
> e.g. XactReadOnly isn't set,
>

Yeah, I think we can add the check for XactReadOnly along with other
checks in CreateReplicationSlot().

> nor do we enforce in an obvious place that we
> don't already hold a snapshot.
>

We have a check for (FirstXactSnapshot == NULL) in
RestoreTransactionSnapshot->SetTransactionSnapshot. Won't that be
sufficient?

-- 
With Regards,
Amit Kapila.

Commits

Same data as JSON: GET /api/v1/messages/:b64id/commits the thread's linked commits as JSON, with link sources. API reference →

  1. Fix a race condition in updating procArray->replication_slot_xmin.

  2. Don't retreat slot's confirmed_flush LSN.

  3. Add additional checks while creating the initial decoding snapshot.