To: Bill Moran <wmoran@collaborativefusion.com>
cc: tarcizioab@c3sl.ufpr.br, pgsql-performance@postgresql.org
Subject: Re: Difference between "Explain analyze" and "\timing" 
In-reply-to: <20080730205922.ba73b732.wmoran@collaborativefusion.com> 
References: <50061.201.15.49.76.1217463555.squirrel@webmail.inf.ufpr.br>
	<20080730205922.ba73b732.wmoran@collaborativefusion.com>
Comments: In-reply-to Bill Moran <wmoran@collaborativefusion.com>
	message dated "Wed, 30 Jul 2008 20:59:22 -0400"
Date: Wed, 30 Jul 2008 21:06:38 -0400
Message-ID: <26508.1217466398@sss.pgh.pa.us>
From: Tom Lane <tgl@sss.pgh.pa.us>

Bill Moran <wmoran@collaborativefusion.com> writes:
> tarcizioab@c3sl.ufpr.br wrote:
>> The commands "\timing" and "EXPLAIN ANALYZE" return values related to the
>> time of execution of the instruction. These values are "Time:" and "Total
>> runtime:" respectively. What is the difference between these values, and
>> the specific use of each command in queries?

> The time reported by explain will be the time it took the server to
> execute the query.

> The time reported by \timing is the time it takes the client (psql) to
> get the result.  This will be the time the server took, plus any network
> delays and time required to process the query and result on the client
> side.

Also realize that explain analyze only reports the time to *execute*
the query.  Not counted are the time to parse and plan the query
beforehand and prepare the explain output afterwards.  But psql's number
is the whole round-trip time and so includes all that stuff.

If any of this seems confusing, you might find it worth reading
this overview of the Postgres system structure:
http://www.postgresql.org/docs/8.3/static/overview.html

			regards, tom lane