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From: Greg Stark on 29 May 2010 22:56
This sounds familiar. If you search back in the archives around 2004
or so I think you'll find a similar discussion when we replaced the
crc32 implementation with what we have now. We put a fair amount of
effort into searching for faster implementations so if you've found
one 3x faster I'm pretty startled. Are you sure it's faster on all
architectures and not a win sometimes and a loss other times? And are
you sure it's faster in our use case where we're crcing small
sequences of data often and not crcing a large block?

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From: Tom Lane on 29 May 2010 23:54
Greg Stark <gsstark(a)mit.edu> writes:
> On Sun, May 30, 2010 at 3:56 AM, Greg Stark <gsstark(a)mit.edu> wrote:
>> This sounds familiar. If you search back in the archives around 2004
>> or so I think you'll find a similar discussion when we replaced the
>> crc32 implementation with what we have now.

> Fwiw here's the thread (from 2005):
> http://thread.gmane.org/gmane.comp.db.postgresql.devel.general/43811

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.

regards, tom lane

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From: Greg Stark on 29 May 2010 23:01
On Sun, May 30, 2010 at 3:56 AM, Greg Stark <gsstark(a)mit.edu> wrote:
> This sounds familiar. If you search back in the archives around 2004
> or so I think you'll find a similar discussion when we replaced the
> crc32 implementation with what we have now.

Fwiw here's the thread (from 2005):

http://thread.gmane.org/gmane.comp.db.postgresql.devel.general/43811
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From: Greg Stark on 30 May 2010 12:29
On Sun, May 30, 2010 at 4:54 AM, Tom Lane <tgl(a)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.

Alright, how about this thread?

http://thread.gmane.org/gmane.comp.db.postgresql.devel.general/71741

This actually sounds like precisely the same algorithm. Perhaps this
implementation is much better but your tests on the old one showed a
big difference between smaller and larger data sequences.


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From: Greg Stark on 30 May 2010 12:43
On Sun, May 30, 2010 at 5:29 PM, Greg Stark <gsstark(a)mit.edu> wrote:
> On Sun, May 30, 2010 at 4:54 AM, Tom Lane <tgl(a)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.
>
> Alright, how about this thread?
>
> http://thread.gmane.org/gmane.comp.db.postgresql.devel.general/71741

Huh, actually apparently this is right about on schedule for
reconsidering this topic:

http://article.gmane.org/gmane.comp.db.postgresql.devel.general/71903

:)

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