Performance of UNION vs IN

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От Jean-Max Reymond
Тема Performance of UNION vs IN
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Msg-id 532B1E05.70409@free.fr
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Ответы Re: Performance of UNION vs IN  (Torsten Förtsch)
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I have a very complex view zinfoexp and running the view as:
SELECT * FROM zinfoexp  WHERE idmembre in (1,84)
take 2700 ms

So, I try another syntax:
SELECT * FROM zinfoexp  WHERE idmembre = 1
union
SELECT * FROM zinfoexp  WHERE idmembre = 84

and for me, two calls to my view takes a lot of time (may be x2) and it
takes 134 ms !

How is it possible that the optimizer cannot optimize the IN as UNION ?
I have a database postgresql 9.3  freshly vacuumed

--
Jean-Max Reymond
CKR Solutions Open Source http://www.ckr-solutions.com


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