Re: unstable SELECT performance under load

On Tue, Dec 9, 2008 at 3:35 PM, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
> Piotr Foremniak <piotr(dot)foremniak(at)gmail(dot)com> writes:
>> When executing some quite complex select queries our 8.3.5 Postgres
>> often hangs. The query that we used to reproduce this problem on our
>> isolated test environment is a quite complex join of ca.15 tables.
>> When executed only once, it always takes ca. 500ms to finish. When
>> executed by a JMeter stress test running a couple of threads
>> simultaneously, ca. 95% of queries also take 500ms to finish. In the
>> remaining 5% cases something weird happens and the same query finishes
>> after several minutes, with the postgres process generating gigabytes
>> of temp files and consuming 100% processor resources.
>
> Hmm, are you *sure* you have geqo = off? Because this sure sounds like

It might have gotten turned on for the user or database so even if
it's set that way in postgresql.conf doesn't mean it's not happening.