On Thu, Apr 23, 2015 at 9:03 PM, Michael Paquier <michael.paqu...@gmail.com> wrote: > 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.
What are those cases? To me that sounds like making things complicated to no obvious benefit. -- Robert Haas EnterpriseDB: http://www.enterprisedb.com The Enterprise PostgreSQL Company -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
