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From: Pierre C <lists@peufeu.com>
To: Josh Berkus <josh@agliodbs.com>
To: Tobias Brox <tobixen@gmail.com>
Cc: pgsql-performance@postgresql.org, "Mladen Gogala" <mladen.gogala@vmsinfo.com>
Subject: Re: Why we don't want hints Was: Slow count(*) again...
Date: Fri, 11 Feb 2011 15:51:44 +0100
Message-ID: <op.vqqt8ihaeorkce@apollo13> (raw)
In-Reply-To: <AANLkTikCG8QUGpt7X=WEBnQCOio=R=zMLa_AoH4KCG2J@mail.gmail.com>
References: <201102012247.p11Ml6u02682@momjian.us>
	<4D489AD1.1010105@vmsinfo.com>
	<AANLkTiknZi97dDwm7sHqy0EL7tpNEP9sY5uPV6AN+q=u@mail.gmail.com>
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	<4D49A6B9.4060608@2ndquadrant.com>
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	<4D4AE16E.9040807@peak6.com>
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	<AANLkTi=6_7N4EuT-trfPbxb9UmanJsnL+ineO-iJUFtJ@mail.gmail.com>
	<4D4B2E8A.7010402@vmsinfo.com>
	<4D4B3395.6010007@agliodbs.com>
	<4D4B394E.9080505@vmsinfo.com>
	<4D4B5A73.3080302@agliodbs.com>
	<AANLkTikCG8QUGpt7X=WEBnQCOio=R=zMLa_AoH4KCG2J@mail.gmail.com>


>    select * from account_transaction where trans_type_id in ( ...
> long, hard-coded list ...) and account_id=? order by created desc
> limit 25;

You could use an index on (account_id, created, trans_type), in  
replacement of your index on (account_id, created). This will not prevent  
the "Index Scan Backwards", but at least, index rows with trans_type not  
matching the WHERE clause will not generate any heap access...



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