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From: Craig Ringer <craig@2ndquadrant.com>
To: Robert Haas <robertmhaas@gmail.com>
Cc: Heikki Linnakangas <hlinnakangas@vmware.com>
Cc: Greg Stark <stark@mit.edu>
Cc: Alvaro Herrera <alvherre@2ndquadrant.com>
Cc: Andres Freund <andres@2ndquadrant.com>
Cc: Bruce Momjian <bruce@momjian.us>
Cc: Rajeev rastogi <rajeev.rastogi@huawei.com>
Cc: Ants Aasma <ants@cybertec.at>
Cc: PostgreSQL-development <pgsql-hackers@postgresql.org>
Cc: Markus Wanner <markus@bluegap.ch>
Subject: Re: Proposal for CSN based snapshots
Date: Wed, 18 Jun 2014 09:00:37 +0800
Message-ID: <53A0E4B5.3090207@2ndquadrant.com> (raw)
In-Reply-To: <CA+TgmoZ8iWw0XstPm5PLPyeRgAjaMk7PT0EXz4qZnj5nx5pKsA@mail.gmail.com>
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	<BF2827DCCE55594C8D7A8F7FFD3AB7713DDBC758@SZXEML508-MBX.china.huawei.com>
	<5370D323.1070606@vmware.com>
	<20140512144112.GB9619@awork2.anarazel.de>
	<5370E267.2020904@vmware.com>
	<20140515183436.GD25053@momjian.us>
	<CA+TgmoYiqga4KWz_1=O8D6ivmTAJfY=-fxO6Nk+D-o3M0M60=Q@mail.gmail.com>
	<20140515200632.GB16014@awork2.anarazel.de>
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	<5388A063.5000209@vmware.com>
	<539E7985.5090801@2ndquadrant.com>
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On 06/18/2014 12:41 AM, Robert Haas wrote:
> On Mon, Jun 16, 2014 at 12:58 AM, Craig Ringer <craig@2ndquadrant.com> wrote:
>> > On 05/30/2014 11:14 PM, Heikki Linnakangas wrote:
>>> >> Yeah. To recap, the failure mode is that if the master crashes and
>>> >> restarts, the transaction becomes visible in the master even though it
>>> >> was never replicated.
>> >
>> > Wouldn't another pg_clog bit for the transaction be able to sort that out?
> How?

A flag to indicate that the tx is locally committed but hasn't been
confirmed by a streaming synchronous replica, so it must not become
visible until the replica confirms it or SR is disabled.

Then scan pg_clog on start / replica connect and ask the replica to
confirm local commit for those tx's.

No?

-- 
 Craig Ringer                   http://www.2ndQuadrant.com/
 PostgreSQL Development, 24x7 Support, Training & Services


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  Cc: craig@2ndquadrant.com, robertmhaas@gmail.com, hlinnakangas@vmware.com, stark@mit.edu, alvherre@2ndquadrant.com, andres@2ndquadrant.com, bruce@momjian.us, rajeev.rastogi@huawei.com, ants@cybertec.at, markus@bluegap.ch
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