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Re: Simple queries take forever to run

From: Stephan Szabo <sszabo(at)megazone(dot)bigpanda(dot)com>
To: Michael Guerin <guerin(at)rentec(dot)com>
Cc: <pgsql-performance(at)postgresql(dot)org>
Subject: Re: Simple queries take forever to run
Date: 2003-08-28 01:22:23
Message-ID: 20030827182051.W85397-100000@megazone.bigpanda.com (view raw or flat)
Thread:
Lists: pgsql-performance
On Wed, 27 Aug 2003, Michael Guerin wrote:

> I'm running into some performance problems trying to execute simple
> queries.
>
> postgresql version 7.3.3
> .conf params changed from defaults.
> shared_buffers = 64000
> sort_mem = 64000
> fsync = false
> effective_cache_size = 400000
>
> ex. query: select * from x where id in (select id from y);
>
> There's an index on each table for id.  SQL Server takes <1s to return,
> postgresql doesn't return at all, neither does explain analyze.

IN(subquery) is known to run poorly in 7.3.x and earlier.  7.4 is
generally much better (for reasonably sized subqueries) but in earlier
versions you'll probably want to convert into an EXISTS or join form.


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Subject: Re: Simple queries take forever to run
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Subject: Re: Queries sometimes take 1000 times the normal time

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