| From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
|---|---|
| To: | "Mark Cave-Ayland" <m(dot)cave-ayland(at)webbased(dot)co(dot)uk> |
| Cc: | "'Simon Riggs'" <simon(at)2ndquadrant(dot)com>, pgsql-hackers(at)postgresql(dot)org |
| Subject: | Re: Cost of XLogInsert CRC calculations |
| Date: | 2005-05-10 14:30:55 |
| Message-ID: | 10161.1115735455@sss.pgh.pa.us |
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| Lists: | pgsql-hackers |
"Mark Cave-Ayland" <m(dot)cave-ayland(at)webbased(dot)co(dot)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.
regards, tom lane
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