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BitMapScan performance degradation

From: Jérôme BENOIS <benois(at)argia-engineering(dot)fr>
To: PostgreSQL Performance <pgsql-performance(at)postgresql(dot)org>
Cc: Xavier Milliard <milliard(at)argia(dot)fr>,Laurent BELMONTE <belmonte(at)argia(dot)fr>
Subject: BitMapScan performance degradation
Date: 2006-11-21 09:21:29
Message-ID: 1164100889.5281.184.camel@localhost.localdomain (view raw or flat)
Thread:
Lists: pgsql-performance
Hi All,

	I have some problems with my sql query :

select distinct
INTEGER_VALUE,DATE_VALUE,EI_ID,VALUE_TYPE,FLOAT_VALUE,ID,TEXT_VALUE,CATEGORY_ID,STRING_VALUE,CATEGORYATTR_ID,NAME from (((  select d_attribute as reqin2 where reqin2.CATEGORYATTR_ID = 1041947543 AND reqin2.TEXT_VALUE ilike '%autrefois%' and ei_id in ( select distinct ei_id as EIID from MPNG2_ei_attribute as reqin3 where reqin3.NAME = 'CategoryID-1084520156' AND reqin3.STRING_VALUE = '1084520156' )  )  ) ) ) as req0 join MPNG2_ei_attribute on req0.eiid = MPNG2_ei_attribute.ei_id   order by ei_id asc;

	When enable_bitmapscan is enabled this query cost 51893.491 ms and when
is disabled 117.709 ms. But i heard bitmapscan feature improved
performance, can you help me ?

	You can read two results of EXPLAIN ANALYZE command here :
http://sharengo.org/explain.txt

Best Regards,
Jérôme.

-- 
Jérôme BENOIS
Open-Source : http://www.sharengo.org
Corporate : http://www.argia-engineering.fr
JabberId : jerome.benois AT gmail.com

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