From: Heikki Linnakangas <hlinnakangas@vmware.com>
To: Linos <info@linos.es>
To: pgsql-performance@postgresql.org
Subject: Re: unneeded joins on view
Date: Wed, 16 Apr 2014 18:57:21 +0300
Message-ID: <534EA861.3020204@vmware.com> (raw)
In-Reply-To: <534E9E14.5000304@linos.es>
References: <534E9E14.5000304@linos.es>
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On 04/16/2014 06:13 PM, Linos wrote:
> I thought that Postgresql would optimize out joins on columns I
> don't ask for when I use the view but it doesn't, this query:
It doesn't, because it would be wrong. It still has to check that the
tables have a matching row (or multiple matching rows).
If you use LEFT JOINs instead, and have a unique index on all the ID
columns, then the planner can do what you expected and leave out the joins.
- Heikki
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To: pgsql-performance@postgresql.org
Cc: hlinnakangas@vmware.com, info@linos.es
Subject: Re: unneeded joins on view
In-Reply-To: <534EA861.3020204@vmware.com>
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