On Thu, Apr 23, 2015 at 10:42 PM, Robert Haas wrote: > On Thu, Apr 23, 2015 at 4:19 AM, Simon Riggs wrote: >> We only need a freeze/backup map for larger relations. So if we map 1000 >> blocks per map page, we skip having a map at all when size < 1000. > > Agreed. We might also want to map multiple blocks per map slot - e.g. > one slot per 32 blocks. That would keep the map quite small even for > very large relations, and would not compromise efficiency that much > since reading 256kB sequentially probably takes only a little longer > than reading 8kB. > > I think the idea of integrating the freeze map into the VM fork is > also worth considering. Then, the incremental backup map could be > optional; if you don't want incremental backup, you can shut it off > and have less overhead.
When I read that I think about something configurable at relation-level.There are cases where you may want to have more granularity of this information at block level by having the VM slots to track less blocks than 32, and vice-versa. -- Michael -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
