Re: Re: [COMMITTERS] pgsql: Avoid extra locks in GetSnapshotData if old_snapshot_threshold <

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От Alvaro Herrera
Тема Re: Re: [COMMITTERS] pgsql: Avoid extra locks in GetSnapshotData if old_snapshot_threshold <
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Msg-id 20160524181144.GA441079@alvherre.pgsql
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Ответ на Re: Re: [COMMITTERS] pgsql: Avoid extra locks in GetSnapshotData if old_snapshot_threshold <  (Kevin Grittner <kgrittn@gmail.com>)
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Kevin Grittner wrote:
> On Tue, May 24, 2016 at 12:00 PM, Andres Freund <andres@anarazel.de> wrote:
>
> > Analyze IIRC acquires a new snapshot when getting sample rows,
>
> I could not find anything like that, and a case-insensitive search
> of analyze.c finds no occurrences of "snap".  Can you remember
> where you think you saw something that would cause the ANALYZE
> command in my test to use a snapshot other than the one from the
> REPEATABLE READ transaction in which it was run?

For ANALYZE, the snapshot is set in vacuum() prior to calling
analyze_rel(); see vacuum.c.

--
Álvaro Herrera                http://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services


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