Re: Inconsistent performance

On Mon, 15 Sep 2003, Joseph Bove wrote:

> I am working with a decent sized database on an extremely powerful machine.
> The specs follow:
>
>     OS:            RedHat Linux 9.0
>     PG Version        7.3
>     Memory        1 gig
>     CPU            Quad Processor - Unsure of exact CPUs
>     Hard Drive        80 gigs
>     Database Size        2 gigs
>
>
> As you can see the server is built for overkill.
>
> The problem that I see is as follows.
>
> I do a rather simple query: select count (*) from large-table where column
> = some value;
>
> About 80% of the time, the response time is sub-second. However, at 10% of
> the time, the response time is 5 - 10 seconds.

Is it consistant for various values of "some value"?  If so, it's possible
that it's switching plans based on the apparent selectivity of the column
for that value.