Re: Undetected corruption of table files

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: "Albe Laurenz" <all(at)adv(dot)magwien(dot)gv(dot)at>
Cc: pgsql-general(at)postgresql(dot)org, pgsql-hackers(at)postgresql(dot)org
Subject: Re: Undetected corruption of table files
Date: 2007-08-27 15:16:55
Message-ID: 617.1188227815@sss.pgh.pa.us
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"Albe Laurenz" <all(at)adv(dot)magwien(dot)gv(dot)at> writes:
> Tom Lane wrote:
>>> Would it be an option to have a checksum somewhere in each
>>> data block that is verified upon read?

>> That's been proposed before and rejected before. See the archives ...

> I searched for "checksum" and couldn't find it. Could someone
> give me a pointer? I'm not talking about WAL files here.

"CRC" maybe? Also, make sure your search goes all the way back; I think
the prior discussions were around the same time WAL was initially put
in, and/or when we dropped the WAL CRC width from 64 to 32 bits.
The very measurable overhead of WAL CRCs are the main thing that's
discouraged us from having page CRCs. (Well, that and the lack of
evidence that they'd actually gain anything.)

regards, tom lane

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