On Mon, 2003-07-14 at 17:13, Jay O'Connor wrote:
> What impact in performance does vacuum have on an active database? I'm
> being asked about this...or rather...someone is questioning the use of
> postgresql because of this
There is no easy answer to this question, other than if you vacuum
appropriately (not to often, or too infrequently) the net impact on
system performance is a win. A database system that doesn't require a
vacuum type process still has to do the same work, it just does it at
transaction time, postgres defers this work until vacuum is run, which
is typically done at off peak times.
As the author of the pg_autovacuum daemon in 7.4 contrib, I would
suggest you try it :-) The primary advantage of the daemon is that it
monitors activity and when needed, vacuums specific tables, not whole
databases. The thresholds that dictate when vacuums occur can be set at
runtime, and should allow you to get it performing the way you want. If
you have any questions or problems let me know. I am always interested
in hearing about others real world experiences.
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TIP 9: the planner will ignore your desire to choose an index scan if your
joining column's datatypes do not match
