Re: performance drop on 8.2.4, reverting to 8.1.4 - Mailing list pgsql-performance

From Liviu Ionescu
Subject Re: performance drop on 8.2.4, reverting to 8.1.4
Date
Msg-id 008901c79942$e7136e10$653e10ac@ilgvaio
Whole thread Raw
In response to Re: performance drop on 8.2.4, reverting to 8.1.4  ("Steinar H. Gunderson" <sgunderson@bigfoot.com>)
Responses Re: performance drop on 8.2.4, reverting to 8.1.4  ("Steinar H. Gunderson" <sgunderson@bigfoot.com>)
Re: performance drop on 8.2.4, reverting to 8.1.4  ("George Pavlov" <gpavlov@mynewplace.com>)
List pgsql-performance
> 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
orthe 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
encounternew problems? 

regards,

Liviu



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