| From: | Pavan Deolasee <pavan(dot)deolasee(at)gmail(dot)com> |
|---|---|
| To: | Johann Spies <johann(dot)spies(at)gmail(dot)com> |
| Cc: | pgsql-performance <pgsql-performance(at)postgresql(dot)org> |
| Subject: | Re: The same query - much different runtimes |
| Date: | 2014-04-07 10:58:45 |
| Message-ID: | CABOikdPQqi5+DgV_CGuxG91cMojQX7ZQ9sxNx7SXKSiER_EXbg@mail.gmail.com |
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| Lists: | pgsql-performance |
On Mon, Apr 7, 2014 at 3:55 PM, Johann Spies <johann(dot)spies(at)gmail(dot)com> wrote:
>
>
> I then ran the query and the result was produced in about the same time as
> (2945 ms).
>
> What can cause such a huge discrepancy?
>
May be when you reran the query, most of the data blocks were cached either
in the shared buffers or the OS cache. That could drastically improve the
performance. I can see a large number of shared buffer hits in the explain
analyze output of the query ran through psql session.
Thanks,
Pavan
--
Pavan Deolasee
http://www.linkedin.com/in/pavandeolasee
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