| From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
|---|---|
| To: | Heikki Linnakangas <hlinnakangas(at)vmware(dot)com> |
| Cc: | 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 13:08:15 |
| Message-ID: | 8008.1371215295@sss.pgh.pa.us |
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| Lists: | pgsql-hackers |
Heikki Linnakangas <hlinnakangas(at)vmware(dot)com> writes:
> Well, time will tell I guess. The biggest overhead with the checksums is
> exactly the WAL-logging of hint bits.
Refresh my memory as to why we need to WAL-log hints for checksumming?
I just had my nose in the part of the checksum patch that tediously
copies entire pages out of shared buffers to avoid possible instability
of the hint bits while we checksum and write the page. Given that we're
paying that cost, I don't see why we'd need to do any extra WAL-logging
(above and beyond the log-when-freeze cost that we have to pay already).
But I've not absorbed any caffeine yet today, so maybe I'm just missing
it.
regards, tom lane
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