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From: Vincent de Phily <vincent.dephily@mobile-devices.fr>
To: "French, Martin" <frenchm@cromwell.co.uk>
Cc: pgsql-general@postgresql.org, pgsql-performance@postgresql.org
Subject: Re: [PERFORM] DELETE taking too much memory
Date: Fri, 08 Jul 2011 11:20:14 +0200
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On Thursday 07 July 2011 19:54:08 French, Martin wrote:
> How up to date are the statistics for the tables in question?
> 
> What value do you have for effective cache size?
> 
> My guess would be that planner thinks the method it is using is right
> either for its current row number estimations, or the amount of memory
> it thinks it has to play with.

Not very up to date I'm afraid (as shown by the low estimate of deleted rows). 
Table t2 has been insert-only since its re-creation (that's another story), 
while t1 is your classic insert-many, update-recent.

We haven't tweaked effective cache size yet, it's on the TODO... like many 
other things :/
-- 
Vincent de Phily