Herouth Maoz wrote: > First, I'd like to thank Bill and Alvaro as well as you for your replies. > > Quoting Tom Lane: > >Hmm. Given the churn rate on the table, I'm having a very hard time > >believing that you don't need to vacuum it pretty dang often. Maybe the > >direction you need to be moving is to persuade autovac to vacuum it > >*more* often, not less often, so that the time needed to finish each > >vacuum is small enough. > Other than reclaiming disk space, is there any advantage to vacuum? > Is a vacuumed table more efficient? Yeah, it frees up space for new tuples. Whether it does anything or not depends on you having long running transactions; if you do, maybe more frequent vacuuming would just scan the table to no useful purpose. > So far, every time it vacuums - > which is around every 15-20 minutes under load conditions - it slows > down processing. I think perhaps Bill's suggestion of just > scheduling the vacuums myself (e.g. 1-2am, off peak) coupled with > cost-based vacuuming might be a good answer? Unless I'm missing an > important point about vacuuming. I think you should continue with your current vacuuming strategy, or perhaps make it more frequent, not less. To prevent it being a load hog you can set vacuum_cost_delay to some nonzero value. Keep in mind that vacuum_cost_delay affects all vacuuming tasks, including autovacuum, whereas autovacuum_vacuum_cost_delay affects autovacuum but not manually invoked vacuum (including the ones you invoke via cron of course) > Alvaro and Bill both suggested scheduling analyzes on a > minute-by-minute cron. Would this be no different than automatic > analyze? No extra overhead for connection, perhaps? No difference. Autovacuum also uses a connection; the only difference is that it does it internally. -- Alvaro Herrera http://www.CommandPrompt.com/ The PostgreSQL Company - Command Prompt, Inc. -- Sent via pgsql-general mailing list (pgsql-general@xxxxxxxxxxxxxx) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-general
