From: Tomas Vondra <tv@fuzzy.cz>
To: Andy Colson <andy@squeakycode.net>
Cc: Craig Ringer <ringerc@ringerc.id.au>
Cc: pgsql-performance@postgresql.org <pgsql-performance@postgresql.org>
Subject: Re: IN or EXISTS
Date: Wed, 31 Aug 2011 16:19:36 +0200
Message-ID: <cf12201c9c3aa4a29a5c2ed26c7853ce.squirrel@sq.gransy.com> (raw)
In-Reply-To: <4E5E3E5F.4000807@squeakycode.net>
References: <4E5D485F.8060300@squeakycode.net>
<4E5D8F68.4010102@ringerc.id.au>
<4E5E3E5F.4000807@squeakycode.net>
On 31 Srpen 2011, 15:59, Andy Colson wrote:
> I assume:
> Buckets: 16384 Batches: 1 Memory Usage: 4531kB
>
> That means a total of 4.5 meg of ram was used for the hash, so if my
> work_mem was lower than that it would swap? (or choose a different plan?)
Why don't you try that? Just set the work_mem to 1MB or so and run the query.
I think it'll use the same plan but multiple batches - read just part of
the inner table so that the hash table fits into work_mem, scan the outer
table etc. The downside is it'd rescan the outer table several times.
Tomas
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To: pgsql-performance@postgresql.org
Cc: tv@fuzzy.cz, andy@squeakycode.net, ringerc@ringerc.id.au
Subject: Re: IN or EXISTS
In-Reply-To: <cf12201c9c3aa4a29a5c2ed26c7853ce.squirrel@sq.gransy.com>
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