On 04/22/2013 09:25 AM, Ants Aasma wrote: > This leaves lingering doubts about the quality of the checksum. It's > hard if not impossible to prove absence of interesting patterns that > would trigger collisions. I do know the checksum quality is miles > ahead of the Fletcher sum originally proposed and during the last week > I haven't been able to think of a way to make the collision rate > significantly differ from CRC.
When we originally discussed this feature, we were potentially discussing a checksum algo which produced collisions for 1 out of 256 pages. That approach was considered acceptable, since it would be very unlikely for such a collision to occur across multiple corrupted pages, and fairly rare to have only one corrupted page. So my perspective is, if we're doing better than 1 in 256, it's good enough. -- Josh Berkus PostgreSQL Experts Inc. http://pgexperts.com -- Sent via pgsql-hackers mailing list (firstname.lastname@example.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers