From: Khangelani Gama <kgama@argility.com>
To: Thomas Kellerer <spam_eater@gmx.net>
To: pgsql-admin@postgresql.org
Subject: Re: Postgres 9 : - How to interpret the EXPLAIN query results
Date: Wed, 25 Mar 2015 13:34:35 +0200
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-----Original Message-----
From: pgsql-admin-owner@postgresql.org
[mailto:pgsql-admin-owner@postgresql.org] On Behalf Of Thomas Kellerer
Sent: 25 March 2015 01:05 PM
To: pgsql-admin@postgresql.org
Subject: Re: [ADMIN] Postgres 9 : - How to interpret the EXPLAIN query
results
Khangelani Gama schrieb am 25.03.2015 um 11:28:
> Thanks to all, but if this total cost is the total time it will take to
> retrieve the output then is it in minutes or milliseconds?
> If it’s in milliseconds does it mean that it take about 213 hrs for a
> total of 768375132.77
No. The cost is not the total time.
Quote from the manual
measured in cost units that are arbitrary, but conventionally mean disk
page fetches
In general you can _assume_ that a query with a higher cost is likely to run
longer than an equivalent query with lower costs.
If you want the runtime of each step you need to use "explain (analyze)" -
again this is documented in the manual.
Thomas
Many Thanks Thomas
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Subject: Re: Postgres 9 : - How to interpret the EXPLAIN query results
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