Re: Inconsistent performance

On Mon, Sep 15, 2003 at 17:34:12 -0400,
  Joseph Bove <jbove@vetstar.com> wrote:
>
> 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.
>
> This is nothing readily apparent at the system level that comes close to
> explaining the performance hits. CPU and memory usage (as measured by top)
> appear to be fine.
>
> Although there are certain tuning issues within the database itself, no
> documentation I have seen seems to indicate that tuning issues would lead
> to such inconsistent response time.

Looking at the output from explain analyze for the query would be useful.
It may be that there are a lot of rows that have the value in the problem
queries.