Subject: Re: Hot Standby on git
From: Simon Riggs <simon@2ndQuadrant.com>
To: Heikki Linnakangas <heikki.linnakangas@enterprisedb.com>
Cc: pgsql-hackers <pgsql-hackers@postgresql.org>
In-Reply-To: <4AC5B92A.7090508@enterprisedb.com>
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Date: Fri, 02 Oct 2009 11:46:51 +0100
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On Fri, 2009-10-02 at 11:26 +0300, Heikki Linnakangas wrote:
> Simon Riggs wrote:
> > On Fri, 2009-10-02 at 10:43 +0300, Heikki Linnakangas wrote:
> > 
> >> It seems dangerous to write a WAL record after the shutdown checkpoint.
> >> It will be overwritten by subsequent startup, which is a recipe for trouble.
> > 
> > I've said its a corner case and not worth spending time on. I'm putting
> > it in at your request. If it's not correct before and not correct after,
> > where exactly do you want it?
> 
> I don't know. Perhaps it should go between the REDO pointer of the
> shutdown checkpoint and the checkpoint record itself. Or maybe the
> information should be included in the checkpoint record itself.

I've implemented this but it requires us to remove two checks - one at
shutdown and one at startup on a shutdown checkpoint. I'm not happy
doing that and would like to put them back.

I'd rather just skip this for now. It's a minor case anyway and there's
nothing stopping writing their own RunningXactData records with a
function, if it is needed. I can add a function for that.

-- 
 Simon Riggs           www.2ndQuadrant.com