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. And in a much better way. And yeah, doing a vacuum placeholder wouldn't be simple, but it's the only solution I can think of that's worthwhile. Just disabling the vacuum releases sharelock behavior puts the user in the situation of deciding between maintenance and uptime. -- Josh Berkus PostgreSQL Experts Inc. http://pgexperts.com -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
