On Tue, Aug 12, 2014 at 10:30 AM, Andres Freund <andres@2ndquadrant.com> wrote:
>> Still not safe. Checksum collisions do happen, especially in big data sets.
>
> If you use an appropriate algorithm for appropriate amounts of data
> that's not a relevant concern. You can easily do different checksums for
> every 1GB segment of data. If you do it right the likelihood of
> conflicts doing that is so low it doesn't matter at all.
True, but if you use LSNs the likelihood is 0. Comparing the LSN is
also most likely a heck of a lot faster than checksumming the entire
page.
--
Robert Haas
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company