On Fri, Aug 12, 2016 at 9:01 AM, Tom Lane <t...@sss.pgh.pa.us> wrote: > Michael Paquier <michael.paqu...@gmail.com> writes: >> In short, autovacuum will need to scan by itself the VM of each >> relation and decide based on that. > > That seems like a worthwhile approach to pursue. The VM is supposed to be > small, and if you're worried it isn't, you could sample a few pages of it. > I do not think any of the ideas proposed so far for tracking the > visibility percentage on-the-fly are very tenable. >
The one visibility map page can store the information of 32672 heap pages (255MB), but it would be cost if autovacuum scan whole visibility map for all tables. So I think that it's better to provide autovacuum_vacuum_pagevisible_factor as a relopts. And the autovacuum scans or samples the visibility map of table that autovacuum_vacuum_pagevisible_factor is set. Regards, -- Masahiko Sawada -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
