Actually, it's inconsistent with the exact same command. I've now replicated the problem by doing the following command:

select count (*) from table;

The table in question has 88899 rows.

The response time is anywhere from 1 second to 12 seconds. Different response times can occur in the same minute of testing!



At 02:34 PM 9/15/2003 -0700, you wrote:
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.

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