Re: performance drop on 8.2.4, reverting to 8.1.4

From: "Liviu Ionescu" <ilgb(at)livius(dot)net>
To: <pgsql-performance(at)postgresql(dot)org>
Subject: Re: performance drop on 8.2.4, reverting to 8.1.4
Date: 2007-05-18 11:51:42
Message-ID: 008901c79942$e7136e10$653e10ac@ilgvaio
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> This seems to be the source of the misestimation. You might
> want to try using "n WHERE n.nodein NOT IN (SELECT nodeid
> FROM templates)" instead of "n LEFT JOIN templates USING
> (nodeid) WHERE templates.nodeid IS NULL" and see if it helps.

it helped, the new version of the query takes 2303 ms on both 8.1.4 and 8.2.4.

any idea why the 8.2.4 planner is not happy with the initial select? was it just a big chance that it worked in 8.1.4 or the 8.2.4 planner has a problem?

or, from another perspective, is the new syntax more portable? what are the chances that after upgrading to 8.3.x to encounter new problems?

regards,

Liviu

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