From: A. Kretschmer <andreas.kretschmer@schollglas.com>
To: pgsql-performance@postgresql.org
Subject: Re: Air-traffic benchmark
Date: Thu, 7 Jan 2010 14:59:00 +0100
Message-ID: <20100107135900.GC9884@a-kretschmer.de> (raw)
In-Reply-To: <852badbc1001070540v6f4f799dyae246d39977fa34f@mail.gmail.com>
References: <852badbc1001070438j36eb10d3qa22398ffcbef405f@mail.gmail.com>
<20100107133225.GB9884@a-kretschmer.de>
<852badbc1001070540v6f4f799dyae246d39977fa34f@mail.gmail.com>
In response to Lefteris :
> Thank you all for your answers!
>
> Andrea, I see the other way around what you are saying:
>
> Sort (cost=7407754.12..7407754.13 rows=4 width=2) (actual
> time=371188.821..371188.823 rows=7 loops=1)
> Seq Scan on ontime (cost=0.00..7143875.40 rows=52775727 width=2)
> (actual time=190938.959..346180.079 rows=52484047 loops=1)
>
>
> I dont see the seq scan to ba a problem, and it is the correct choice
> here because Year spans from 1999 to 2009 and the query asks from 2000
> and on, so PG correctly decides to use seq scan and not index access.
Thats right.
But this is not a contradiction, this seq-scan *is* the real problem, not
the sort. And yes, as others said, increment the work_mem isn't the
solution. It is counterproductive, because you lost buffer-cache.
Andreas, note the 's' at the end ;-)
--
Andreas Kretschmer
Kontakt: Heynitz: 035242/47150, D1: 0160/7141639 (mehr: -> Header)
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To: pgsql-performance@postgresql.org
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Subject: Re: Air-traffic benchmark
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