| From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
|---|---|
| To: | Aidan Van Dyk <aidan(at)highrise(dot)ca> |
| Cc: | Alvaro Herrera <alvherre(at)commandprompt(dot)com>, Martijn van Oosterhout <kleptog(at)svana(dot)org>, Greg Stark <greg(dot)stark(at)enterprisedb(dot)com>, Heikki Linnakangas <heikki(dot)linnakangas(at)enterprisedb(dot)com>, Gregory Stark <stark(at)enterprisedb(dot)com>, Pg Hackers <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: Block-level CRC checks |
| Date: | 2008-11-18 17:40:38 |
| Message-ID: | 21637.1227030038@sss.pgh.pa.us |
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| Lists: | pgsql-hackers |
Aidan Van Dyk <aidan(at)highrise(dot)ca> writes:
> But why can't you wal-log the hint bits from the "buffered" page. then your
> consitent. At least as consistent as the original write was.
> So you're CRC ends up being:
> Buffer the page
> Calculate CRC on the buffered page
> WAL (in bulk) the hint bits (and maybe CRC?)
> write buffered page
The trouble here is to avoid repeated WAL-logging of the same hint bits.
(Alvaro's patch tried to do that by depending on another hint bit in the
page header, but that seems unsafe if hint bit setters aren't taking
exclusive lock.)
regards, tom lane
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