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Re: How to interpret this explain analyse?

From: "Joost Kraaijeveld" <J(dot)Kraaijeveld(at)Askesis(dot)nl>
To: "Tom Lane" <tgl(at)sss(dot)pgh(dot)pa(dot)us>
Cc: "Richard Huxton" <dev(at)archonet(dot)com>,"Pgsql-Performance (E-mail)" <pgsql-performance(at)postgresql(dot)org>
Subject: Re: How to interpret this explain analyse?
Date: 2005-02-11 23:12:26
Message-ID: A3D1526C98B7C1409A687E0943EAC41048A15A@obelix.askesis.nl (view raw or flat)
Thread:
Lists: pgsql-performance
Hi Tom,

Tom Lane schreef:
> Well, the planner does put some emphasis on startup time when dealing
> with a DECLARE CURSOR plan; the problem you face is just that that
> correction isn't large enough.  (From memory, I think it optimizes on
> the assumption that 10% of the estimated rows will actually
> be fetched; you evidently want a setting of 1% or even less.)
I wish I had your mnemory ;-) . The tables contain 1.100.000 records by the way  (that is not nearly 10 %, my math is not that good))


> We once talked about setting up a GUC variable to control the
> percentage of a cursor that is estimated to be fetched:
> http://archives.postgresql.org/pgsql-hackers/2000-10/msg01108.php
> It never got done but that seems like the most reasonable solution to
> me. 
If the proposal means that the cursor is not limited to ths limit in the query but is limited to the fetch than I support the proposal. A bit late I presume.

Groeten,

Joost Kraaijeveld
Askesis B.V.
Molukkenstraat 14
6524NB Nijmegen
tel: 024-3888063 / 06-51855277
fax: 024-3608416
e-mail: J(dot)Kraaijeveld(at)Askesis(dot)nl
web: www.askesis.nl

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