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From: Tom Lane <tgl@sss.pgh.pa.us>
To: Dmitry Karasik <dmitry@karasik.eu.org>
cc: pgsql-performance@postgresql.org
Subject: Re: seqscan on UNION'ed views
In-reply-to: <20130227100352.GA46292@nataraj.karasik.eu.org>
References: <20130227100352.GA46292@nataraj.karasik.eu.org>
Comments: In-reply-to Dmitry Karasik <dmitry@karasik.eu.org>
	message dated "Wed, 27 Feb 2013 11:03:52 +0100"
Date: Wed, 27 Feb 2013 09:21:18 -0500
Message-ID: <17937.1361974878@sss.pgh.pa.us>
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Dmitry Karasik <dmitry@karasik.eu.org> writes:
> I need to have a sort of a time machine, where select statements on tables
> could be easily replaced to select statements on tables as they were some time in the past, 
> including all related table. To do so, I used views (see in the script) that UNION
> both current and archive tables and filter them by a timestamp.

If you use UNION ALL instead of UNION, you should get better results
(as well as inherently cheaper queries, since no duplicate-elimination
step will be needed).

			regards, tom lane


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