From: | David Johnston <polobo(at)yahoo(dot)com> |
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To: | pgsql-general(at)postgresql(dot)org |
Subject: | Re: Problem with left join when moving a column to another table |
Date: | 2013-06-21 04:28:26 |
Message-ID: | 1371788906658-5760255.post@n5.nabble.com |
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Thread: | |
Lists: | pgsql-general |
Jason Long-2 wrote
> Does the syntax you showed me have performance benefits vs joining a
> bunch of views together?
As a general rule CTE/WITH is going to be worse performing than the
equivalent view definition - depending on the view is actually used in the
query of course. They both have their place. A CTE/WITH is basically a
per-query VIEW though there is an optimization barrier that doesn't allow
the main query WHERE clause to limit the queries like it a view would
normally allow if possible. Because of this I'll occasionally find need to
specify redundant where clauses inside the CTE to get decent performance on
large tables - mostly for my interactive queries.
David J.
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