On Tue, Mar 4, 2014 at 6:57 AM, Simon Riggs <si...@2ndquadrant.com> wrote: > The main impact I see is that this would block VACUUM while pg_dump runs. > > But then, while pg_dump runs VACUUM is ineffective anyway so perhaps > that is no bad thing.
Well, a vacuum that's already running when pg_dump starts up may be doing a lot of good, so it would be a shame to see pg_dump kill them all off. Also, this would put us in the surprising situation that you can't run two simultaneous dumps of overlapping sets of tables, which doesn't strike me as a great thing. I'd really like to see us find a way to apply some version of this patch. I was in favor of the concept 3 years ago when we did this the first time, and I've subsequently done quite a bit of work (viz., MVCC catalog snapshots) to eliminate the main objection that was raised at that time. But it's really hard to reason about what might happen with lowered lock levels, and convince yourself that there's absolutely nothing that can ever go wrong. I don't know what to do about that tension, but I think even modest improvements in this area stand to benefit an awful lot of users. -- 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