On Mon, Oct 26, 2015 at 4:39 AM, Jim Nasby <jim.na...@bluetreble.com> wrote: > On 10/22/15 6:39 PM, Alvaro Herrera wrote: >> >> Jim Nasby wrote: >> >>> That would be the minimal-impact version, yes. But I suspect if we went >>> through the trouble to do that, it would be just as easy to attempt the >>> freeze regardless of what scan_all is set to. >> >> >> You mean if !scan_all we conditional-get the cleanup lock, if we get it >> then prune, if not then freeze? That seems nice on paper but I think >> it's useless because unless scan_all is true, then relfrozenxid doesn't >> advance anyway. > > > Actually, advancing relfrozenxid only depends on having hit all pages in the > table, which can happen even if !scan_all. Aside from that, once the freeze > map hits this would be useful in setting bits there.
Yeah, when the all pages have frozen totally (that is, when scanned_page + vm_skipped_frozen_page equals relpages), relfrozenxid will be updated. But the item pointers of page that are frozen by such logic are never pruned. 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
