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Re: UNION and bad performance

From: pasman pasmański <pasman(dot)p(at)gmail(dot)com>
To: pgsql-performance(at)postgresql(dot)org
Subject: Re: UNION and bad performance
Date: 2010-12-12 13:12:59
Message-ID: AANLkTikoRUG9qJv0wZVq-n_RKDX0kOqve3PTKjPwc_MZ@mail.gmail.com (view raw or flat)
Thread:
Lists: pgsql-performance
> UNION will remove all duplicates, so that the result additionally requires to
> be sorted.

>Right, to avoid the SORT and UNIQUE - operation you can use UNION ALL


by the way maybe apply hashing to calculate UNION be better ?


------------
pasman

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