Re: Poor query plan across OR operator

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От Tom Lane
Тема Re: Poor query plan across OR operator
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Msg-id 14275.1264524114@sss.pgh.pa.us
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Ответ на Poor query plan across OR operator  (Mark Hills <Mark.Hills@framestore.com>)
Ответы Re: Poor query plan across OR operator  (Robert Haas <robertmhaas@gmail.com>)
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Mark Hills <Mark.Hills@framestore.com> writes:
> One of our most-used queries performs poorly (taking over 2 seconds) and a
> tiny amount of refactoring shows it can be fast (less than 1ms) by
> transforming the OR case (which spans two tables) into a UNION.

I'd suggest going with the UNION.  We are unlikely to make the planner
look for such cases, because usually such a transformation would be a
net loss.  It seems like rather a corner case that it's a win even on
your example.

            regards, tom lane

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