On 2013-04-13 09:14:26 -0400, Bruce Momjian wrote: > On Fri, Apr 12, 2013 at 02:38:27PM -0700, Jeff Davis wrote: > > In general, we have more flexibility with WAL because there is no > > upgrade issue. It would be nice to share code with the data page > > checksum algorithm; but really we should just use whatever offers the > > best trade-off in terms of complexity, performance, and error detection > > rate. > > > > I don't think we need to decide all of this right now. Personally, I'm > > satisfied having SIMD checksums on data pages now and leaving WAL > > optimization until later. > > As I understand it, SIMD is just a CPU-optimized method for producing a > CRC checksum. Is that right? Does it produce the same result as a > non-CPU-optimized CRC calculation?
No we are talking about a different algorithm that results in different results, thats why its important to choose now since we can't change it later without breaking pg_upgrade in further releases. http://en.wikipedia.org/wiki/SIMD_%28hash_function%29 Greetings, Andres Freund -- Andres Freund http://www.2ndQuadrant.com/ PostgreSQL Development, 24x7 Support, Training & Services -- Sent via pgsql-hackers mailing list (email@example.com) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers