Re: Cost of XLogInsert CRC calculations

Tom Lane wrote:
> "Mark Cave-Ayland" <m.cave-ayland@webbased.co.uk> writes:
> > I was just researching some articles on compression (zlib) and I saw mention
> > of the Adler-32 algorithm which is supposed to be slightly less accurate
> > than an equivalent CRC calculation but significantly faster to compute. I
> > haven't located a good paper comparing the error rates of the two different
> > checksums,
> 
> ... probably because there isn't one.  With all due respect to the Zip
> guys, I doubt anyone has done anywhere near the analysis on Adler-32
> that has been done on CRCs.  I'd much prefer to stick with true CRC
> and drop it to 32 bits than go with a less-tested algorithm.  Throwing
> more bits at the problem doesn't necessarily create a safer checksum.

Agreed.  64-bit was overkill when we added it, and it is now shown to be
a performance problem.

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