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Re: UNION and bad performance - Mailing list pgsql-performance

From pasman pasmański
Subject Re: UNION and bad performance
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Msg-id AANLkTikoRUG9qJv0wZVq-n_RKDX0kOqve3PTKjPwc_MZ@mail.gmail.com
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In response to UNION and bad performance  (Olivier Pala <olivier.pala@xgs-france.com>)
Responses Re: UNION and bad performance  (Robert Haas <robertmhaas@gmail.com>)
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> 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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