| From: | Florian Pflug <fgp(at)phlo(dot)org> |
|---|---|
| To: | Jeff Davis <pgsql(at)j-davis(dot)com> |
| Cc: | Greg Smith <greg(at)2ndQuadrant(dot)com>, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Ants Aasma <ants(at)cybertec(dot)at>, Andres Freund <andres(at)2ndquadrant(dot)com>, Bruce Momjian <bruce(at)momjian(dot)us>, Heikki Linnakangas <hlinnakangas(at)vmware(dot)com>, Simon Riggs <simon(at)2ndquadrant(dot)com>, PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: Enabling Checksums |
| Date: | 2013-04-18 17:05:41 |
| Message-ID: | D5C7221E-2913-43CD-8973-1CE21219259A@phlo.org |
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| Lists: | pgsql-hackers |
On Apr18, 2013, at 19:04 , Jeff Davis <pgsql(at)j-davis(dot)com> wrote:
> On Wed, 2013-04-17 at 20:21 -0400, Greg Smith wrote:
>> -Original checksum feature used Fletcher checksums. Its main problems,
>> to quote wikipedia, include that it "cannot distinguish between blocks
>> of all 0 bits and blocks of all 1 bits".
>
> That is fairly easy to fix by using a different modulus: 251 vs 255.
At the expense of a drastic performance hit though, no? Modulus operations
aren't exactly cheap.
best regards,
Florian Pflug
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