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help / color / mirror / Atom feedFrom: Amit Kapila <[email protected]>
To: Tomas Vondra <[email protected]>
Cc: PostgreSQL Hackers <[email protected]>
Subject: Re: sequences vs. synchronous replication
Date: Sun, 19 Dec 2021 08:33:16 +0530
Message-ID: <CAA4eK1KN-Pqe1y5w0uXU2Ttn8DK4WfqgwAbCRbcDt4yzQ88wRA@mail.gmail.com> (raw)
In-Reply-To: <[email protected]>
References: <[email protected]>
On Sat, Dec 18, 2021 at 7:24 AM Tomas Vondra
<[email protected]> wrote:
>
> while working on logical decoding of sequences, I ran into an issue with
> nextval() in a transaction that rolls back, described in [1]. But after
> thinking about it a bit more (and chatting with Petr Jelinek), I think
> this issue affects physical sync replication too.
>
> Imagine you have a primary <-> sync_replica cluster, and you do this:
>
> CREATE SEQUENCE s;
>
> -- shutdown the sync replica
>
> BEGIN;
> SELECT nextval('s') FROM generate_series(1,50);
> ROLLBACK;
>
> BEGIN;
> SELECT nextval('s');
> COMMIT;
>
> The natural expectation would be the COMMIT gets stuck, waiting for the
> sync replica (which is not running), right? But it does not.
>
How about if we always WAL log the first sequence change in a transaction?
--
With Regards,
Amit Kapila.
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Subject: Re: sequences vs. synchronous replication
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