From: | Robert Haas <robertmhaas(at)gmail(dot)com> |
---|---|
To: | Dave Johansen <davejohansen(at)gmail(dot)com> |
Cc: | pgsql-performance(at)postgresql(dot)org |
Subject: | Re: Pushing LIMIT into sub-queries of a UNION ALL |
Date: | 2011-05-23 17:21:17 |
Message-ID: | BANLkTi=kf74TbkbZpxuFQmE_Y9yXpHizzw@mail.gmail.com |
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Lists: | pgsql-performance |
On Mon, May 16, 2011 at 3:38 PM, Dave Johansen <davejohansen(at)gmail(dot)com> wrote:
> I am using Postgres 8.3 and I have an issue very closely related to the one
> described here:
> http://archives.postgresql.org/pgsql-general/2005-06/msg00488.php
>
> Basically, I have a VIEW which is a UNION ALL of two tables but when I do a
> select on the view using a LIMIT, it scans the entire tables and takes
> significantly longer than writing out the query with the LIMITs in the
> sub-queries themselves. Is there a solution to get the view to perform like
> the sub-query version?
I believe this is fixed by MergeAppend in 9.1. You might want to try
9.1beta1 and see if that works better for you.
--
Robert Haas
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company
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