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Message-ID: <5047FBA8.1030909@ringerc.id.au>
Date: Thu, 06 Sep 2012 11:26:00 +1000
From: Craig Ringer <ringerc@ringerc.id.au>
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To: Anibal David Acosta <aa@devshock.com>
CC: pgsql-performance@postgresql.org
Subject: Re: query performance, where goes time?
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On 09/06/2012 07:48 AM, Anibal David Acosta wrote:
> Using explain analyze I saw that many of my queries run really fast,
> less than 1 milliseconds, for example the analyze output of a simple
> query over a table with 5millions of records return  "Total runtime:
> 0.078 ms"
>
> But the real time is a lot  more, about 15 ms, in fact the pgadmin show
> this value.
>
> So, where goes the others 14.2 ms?

Client-side latency, time spent transmitting query results, and network 
latency.

You'll see much less difference in queries that take more meaningful 
amounts of time. This query is so fast that timing accuracy will be an 
issue on some systems, and so will scheduler jitter etc.

--
Craig Ringer