Re: Determining scan types

On Tue, Jul 03, 2001 at 10:42:37AM -0400, Sam Tregar wrote:
: On Tue, 3 Jul 2001, Philip Molter wrote:
:
: > What causes this and how can I fix it?
:
: Have you tried a VACUUM ANALYZE? For some reason Postgres isn't able to
: use its indexes fully unless you VACUUM ANALYZE often.
:
: I consider this a bug but I gather the developers are OK with it.

Yes. In fact, I have to VACUUM ANALYZE the tables every half hour on
this constantly running system or else kernel CPU usage rises to
unacceptable levels (another thing I consider a bug). Like I said, in
the middle of the night (probably after one of these analyses), it
switched from using index scans where appropriate to using sequential
scans for everything. If I turn off sequential scans altogether, it
uses the indices, but I don't get the performance of benefits of using
sequential scans when appropriate.

* Philip Molter
* DataFoundry.net
* http://www.datafoundry.net/
* philip(at)datafoundry(dot)net