On Thu, Jul 31, 2014 at 5:26 AM, desmodemone <desmodem...@gmail.com> wrote: > b) yes the backends need to update the map, but it's in memory, and as I > show, could be very small if we you chunk of blocks.If we not compress the > map, I not think could be a bottleneck.
If it's in memory, it's not crash-safe. For something aimed at backups, I think crash safety is a requirement. So it's at least one extra I/O per commit, maybe less if many can be coalesced at checkpoints, but I wouldn't count on it too much, because worst cases are easy to come by (sparse enough updates). I think this could be pegged on WAL replay / checkpoint stuff alone, so it would be very asynchronous, but not free. -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
