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List:       pgsql-performance
Subject:    Re: [PERFORM] Nested Loop join being improperly chosen
From:       Brad Ediger <brad () bradediger ! com>
Date:       2008-08-28 23:22:19
Message-ID: 62A18AAC-9BD9-41FF-AA4F-794D9AB540C6 () bradediger ! com
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On Aug 28, 2008, at 6:01 PM, David Rowley wrote:

> I had a similar problem here:
> http://archives.postgresql.org/pgsql-bugs/2008-07/msg00026.php
>
> Is the nested loop performing a LEFT join with yours? It's a little
> difficult to tell just from the query plan you showed.
>
> A work around for mine was to use a full outer join and eliminate  
> the extra
> rows in the where clause. A bit of a hack but it changed a 2 min  
> query into
> one that ran in under a second.
>
> Of course this is not helping with your problem but at least may  
> trigger
> some more feedback.

Hi David,
Thanks for your input. All of the joins are inner joins; the query is  
a large one with 5 or 6 subqueries. It was being generated from a  
popular data warehousing / business intelligence product whose name I  
shall not mention. The vendor ended up pulling the subselects out into  
SELECT INTO statements on temporary tables. It's kludgey, but it works  
much better.

Thanks,
Brad
["smime.p7s" (smime.p7s)]

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