From: Jochen Erwied <jochen@pgsql-performance.erwied.eu>
To: Lefteris <lsidir@gmail.com>
Cc: pgsql-performance@postgresql.org
Subject: Re: Air-traffic benchmark
Date: Thu, 7 Jan 2010 15:05:35 +0100
Message-ID: <26014999.20100107150535@erwied.eu> (raw)
In-Reply-To: <852badbc1001070547p48b47175vf87efc473e3bd41b@mail.gmail.com>
References: <852badbc1001070438j36eb10d3qa22398ffcbef405f@mail.gmail.com>
<4B45E36E.4040706@tweakers.net>
<852badbc1001070547p48b47175vf87efc473e3bd41b@mail.gmail.com>
Thursday, January 7, 2010, 2:47:36 PM you wrote:
> so I understand from all of you that you don't consider the use of 25k
> for sorting to be the cause of the slowdown? Probably I am missing
Maybe you are reading the plan wrong:
- the sort needs only 25kB of memory, and finishes in sub-second time,
mainly because the sort only sorts the already summarized data, and not
the whole table
- the sequential scan takes 346 seconds, and thus is the major factor in
time to finish!
So the total query time is 371 seconds, of which 346 are required to
completely scan the table once.
--
Jochen Erwied | home: jochen@erwied.eu +49-208-38800-18, FAX: -19
Sauerbruchstr. 17 | work: joe@mbs-software.de +49-2151-7294-24, FAX: -50
D-45470 Muelheim | mobile: jochen.erwied@vodafone.de +49-173-5404164
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To: pgsql-performance@postgresql.org
Cc: jochen@pgsql-performance.erwied.eu, lsidir@gmail.com
Subject: Re: Air-traffic benchmark
In-Reply-To: <26014999.20100107150535@erwied.eu>
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