From: Michal Taborsky - Internet Mall <michal.taborsky@mall.cz>
To: pgsql-performance@postgresql.org
Subject: Re: 3-table query optimization
Date: Thu, 10 Aug 2006 09:30:35 +0200
Message-ID: <44DAE09B.20009@mall.cz> (raw)
In-Reply-To: <20367.1155136139@sss.pgh.pa.us>
References: <44D9EBEB.9010704@mall.cz>
<20367.1155136139@sss.pgh.pa.us>
Tom Lane napsal(a):
> Michal Taborsky - Internet Mall <michal.taborsky@mall.cz> writes:
>> SELECT product.product_id
>> FROM action
>> JOIN product ON (product.product_id=action.product_id)
>> WHERE action.shop_group_id=1
>> AND EXISTS (SELECT 1
>> FROM catalog.product_program
>> WHERE product_id=product.product_id
>> AND product_program.program_id =1104322
>> )
>
> Try converting the EXISTS subquery to an IN.
The performance is roughly the same. For some groups it's better, for
some groups, the bigger ones, it's a bit worse. I forgot to mention,
that the server is running 8.0.2. Upgrading would be a bit painful, as
it is a 24/7 production system, but if it would help significantly, we'd
give it a go.
--
Michal Táborský
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To: pgsql-performance@postgresql.org
Cc: michal.taborsky@mall.cz
Subject: Re: 3-table query optimization
In-Reply-To: <44DAE09B.20009@mall.cz>
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