On 2014-12-02 11:12:40 -0800, Josh Berkus wrote: > On 12/02/2014 11:08 AM, Andres Freund wrote: > > On 2014-12-02 11:02:07 -0800, Josh Berkus wrote: > >> On 12/02/2014 10:35 AM, Alvaro Herrera wrote: > >>> If the table is large, the time window for this to happen is large also; > >>> there might never be a time window large enough between two lock > >>> acquisitions for one autovacuum run to complete in a table. This > >>> starves the table from vacuuming completely, until things are bad enough > >>> that an emergency vacuum is forced. By then, the bloat is disastrous. > >>> > >>> I think it's that suicide that Andres wants to disable. > > > > Correct. > > > >> A much better solution for this ... and one which would solve a *lot* of > >> other issues with vacuum and autovacuum ... would be to give vacuum a > >> way to track which blocks an incomplete vacuum had already visited. > >> This would be even more valuable for freeze. > > > > That's pretty much a different problem. Yes, some more persistent would > > be helpful - although it'd need to be *much* more than which pages it > > has visited - but you'd still be vulnerable to the same issue. > > If we're trying to solve the problem that vacuums of large, high-update > tables never complete, it's solving the same problem.
Which isn't what I'm talking about. The problem is that vacuum is cancelled if a conflicting lock request is acquired. Plain updates don't do that. But there's workloads where you need more heavyweight updates, and then it can easily happen. Greetings, Andres Freund -- Andres Freund http://www.2ndQuadrant.com/ PostgreSQL Development, 24x7 Support, Training & Services -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers