Re: synchronized snapshots

From: Joachim Wieland <joe(at)mcknight(dot)de>
To: Marko Tiikkaja <marko(dot)tiikkaja(at)2ndquadrant(dot)com>
Cc: pgsql-hackers <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: synchronized snapshots
Date: 2011-09-28 12:25:09
Message-ID: CACw0+12Fh11NnUpa+S3mLPcNOiJtQMUY2_H=RHVDMoN7AYPJ+A@mail.gmail.com
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Hi Marko,

On Wed, Sep 28, 2011 at 2:29 AM, Marko Tiikkaja
<marko(dot)tiikkaja(at)2ndquadrant(dot)com> wrote:
> In a sequence such as this:
>
>  BEGIN TRANSACTION ISOLATION LEVEL SERIALIZABLE;
>  INSERT INTO foo VALUES (-1);
>  SELECT pg_export_snapshot();
>
> the row added to "foo" is not visible in the exported snapshot.  If that's
> the desired behaviour, I think it should be mentioned in the documentation.

Yes, that's the desired behaviour, the patch add this paragraph to the
documentation already:

"Also note that even after the synchronization both clients still run
their own independent transactions. As a consequence, even though
synchronized with respect to reading pre-existing data, both
transactions won't be able to see each other's uncommitted data."

I'll take a look at the other issues and update the patch either
tonight or tomorrow.

Thank you,
Joachim

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