Heikki Linnakangas wrote: > On 11.11.2011 17:47, Tom Lane wrote: > > Robert Haas<robertmh...@gmail.com> writes: > >> On Fri, Nov 11, 2011 at 9:59 AM, Tom Lane<t...@sss.pgh.pa.us> wrote: > >>> It occurs to me to wonder how this scenario will interact with the > >>> recent changes to let VACUUM skip pages. AFAIR there is not a way for a > >>> manual VACUUM to set the anti-wraparound mode, is there? > > > >> I tweaked Simon's original patch to address exactly this scenario; > >> VACUUM FREEZE prevents page-skipping behavior. > > > > That doesn't address my concern. (1) The manual does not say you must > > use VACUUM FREEZE for this, nor do the HINT messages. (2) You probably > > wouldn't want to use VACUUM FREEZE, as that could force a great deal > > more I/O than might be necessary to fix the problem. > > set vacuum_freeze_table_age=0; VACUUM; > > will do the trick. > > > (3) In disaster > > recovery scenarios, the last thing we want is to be imposing extra > > conditions on what an already-stressed DBA has to do to fix things; > > especially extra conditions that are different from the way it's worked > > for the last ten years. > > True. > > > And there's also (4) if someone is doing a > > manual VACUUM, they might well wish the table to be completely vacuumed, > > not just sort of. > > > > I think we'd be better advised to restrict the page-skipping behavior > > to autovacuums, period, and remove the connection to FREEZE. > > Yeah, I think you're right. We can accomplish that by setting the > default vacuum_freeze_age to 0. That way it's still possible to get the > page-skipping behavior in manual VACUUMs by setting it to non-zero, but > you get a full scan by default.
FYI, pg_upgrade needs to use vacuum freeze to remove all references to pg_clog because the files are coming from the old cluster. If we change that, pg_upgrade needs to be adjusted. -- Bruce Momjian <br...@momjian.us> http://momjian.us EnterpriseDB http://enterprisedb.com + It's impossible for everything to be true. + -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers