| From: | Andres Freund <andres(at)2ndquadrant(dot)com> |
|---|---|
| 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 13:39:12 |
| Message-ID: | 20130614133912.GD19500@alap2.anarazel.de |
| Views: | Raw Message | Whole Thread | Download mbox | Resend email |
| Thread: | |
| Lists: | pgsql-hackers |
On 2013-06-14 09:21:52 -0400, Tom Lane wrote:
> Heikki Linnakangas <hlinnakangas(at)vmware(dot)com> writes:
> > On 14.06.2013 16:08, Tom Lane wrote:
> >> Refresh my memory as to why we need to WAL-log hints for checksumming?
>
> > Torn pages:
>
> 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?
MarkBufferDirtyHint() loggs an FPI (just not via a BKP block) via
XLogSaveBufferForHint() iff XLogCheckBuffer() says we need to by
comparing GetRedoRecPtr() with the page's lsn.
Otherwise we don't do anything besides marking the buffer dirty.
Greetings,
Andres Freund
--
Andres Freund http://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Training & Services
| From | Date | Subject | |
|---|---|---|---|
| Next Message | Stephen Frost | 2013-06-14 13:40:51 | Re: MD5 aggregate |
| Previous Message | Heikki Linnakangas | 2013-06-14 13:36:36 | Re: Patch for fail-back without fresh backup |