Re: Patch for fail-back without fresh backup

From: Greg Stark <stark(at)mit(dot)edu>
To: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
Cc: Heikki Linnakangas <hlinnakangas(at)vmware(dot)com>, Pavan Deolasee <pavan(dot)deolasee(at)gmail(dot)com>, Samrat Revagade <revagade(dot)samrat(at)gmail(dot)com>, PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: Patch for fail-back without fresh backup
Date: 2013-06-14 14:39:31
Message-ID: CAM-w4HPNifdXnC0zvUui7C1Q0Rv6j98kR60NNrw3_rbTVRPU3w@mail.gmail.com
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On Fri, Jun 14, 2013 at 2:21 PM, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
> So it's not that we actually need to log the individual hint bit
> changes, it's that we need to WAL-log a full page image on the first
> update after a checkpoint, so as to recover from torn-page cases.
> Which one are we doing?

Wal logging a full page image after a checkpoint wouldn't actually be
enough since subsequent hint bits will dirty the page and not wal log
anything creating a new torn page risk. FPI are only useful if all the
subsequent updates are wal logged.

--
greg

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