Jim C. Nasby wrote:
On Wed, Jan 24, 2007 at 02:37:44PM +0900, Galy Lee wrote:1. How do we know if autovacuum is enough for my application, or should I setup a vacuum manually from cron for my application?Generally I trust autovac unless there's some tables where it's critical that they be vacuumed frequently, such as a queue table or a web session table.
So how much can we trust autovac? I think at least the following cases can not be covered by autovac now:
- small but high update tables which are sensitive to garbage - very big tables which need a long time to be vacuumed. - when we need to adjust the the max_fsm_page
2. How to set the GUC parameters for autovacuum? There are two sets of parameters for autovacuum: - vacuum threshold and scale factor (500/0.2) ?$B!! - analyze threshold and scale factor(250/0.1) Is there any guideline to set these parameters? When does it need to change the default values?I find those are generally pretty good starting points; just bear in mind that it means 20% dead space.
so what is the principle to set them? - keep dead space lower than some disk limit - or keep the garbage rate lower than fillfactor or any other general principle?
