Re: Postgresql 7.4.8 inconsistent index usage

On Fri, Jul 08, 2005 at 12:04:07PM -0400, Stephen Bowman wrote:
>
> Clearly it needs to use the index =)

Indeed -- now to figure out why the estimates for index scans are
so high.  The row count estimates are almost spot-on, so that's not
it.  What are your settings for the following configuration variables?

shared_buffers
random_page_cost
effective_cache_size
cpu_tuple_cost
cpu_index_tuple_cost

How much RAM do you have?  Have you set shared_buffers and
effective_cache_size accordingly?  The default values are pretty
low for most modern equipment; see the following for tips on
choosing appropriate values:

http://www.powerpostgresql.com/PerfList/

You mentioned that you've analyzed the table, but have you also
vacuumed it recently?

BTW, I should have mentioned earlier that this thread might be
on-topic in pgsql-performance.

--
Michael Fuhr
http://www.fuhr.org/~mfuhr/