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Re: Re: [RFC][PATCH]: CRC32 is limiting at COPY/CTAS/INSERT ... SELECT + speeding it up

Florian Pflug <fgp@phlo.org>

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From: Florian Pflug <fgp@phlo.org>
To: Andres Freund <andres@anarazel.de>
Cc: "Pierre C" <lists@peufeu.com>, "Greg Stark" <gsstark@mit.edu>, "Tom Lane" <tgl@sss.pgh.pa.us>, "Bruce Momjian" <bruce@momjian.us>, pgsql-hackers@postgresql.org, singh.gurjeet@gmail.com
Date: 2010-06-07T12:10:30Z
Lists: pgsql-hackers 
On Jun 7, 2010, at 12:45 , Andres Freund wrote:
> On Monday 07 June 2010 12:37:13 Pierre C wrote:
>>> On Sunday 30 May 2010 18:29:31 Greg Stark wrote:
>>>> On Sun, May 30, 2010 at 4:54 AM, Tom Lane <tgl@sss.pgh.pa.us> wrote:
>>>>> I read through that thread and couldn't find much discussion of
>>>>> alternative CRC implementations --- we spent all our time on arguing
>>>>> about whether we needed 64-bit CRC or not.
>> 
>> SSE4.2 has a hardware CRC32 instruction, this might be interesting to
>> use...
> Different polynom unfortunately...

Since only the WAL uses CRC, I guess the polynomial could be changed though. pg_upgrade for example shouldn't care.

RFC3385 compares different checksumming methods for use in iSCSI, and CRC32c (which uses the same polynomial as the SSE4.2 instruction) wins. Here's 
a link: http://www.faqs.org/rfcs/rfc3385.html

best regards,
Florian Pflug