Обсуждение: WHERE order

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WHERE order

От
Rod Taylor
Дата:
It would appear that in 7.4 the order of clauses in WHERE affects the
execution time (not output if AND).

I would think that a simple optimization would be to push off evaluation
of a subplan whenever possible by re-arranging AND statements.

In the below example, it gives an order of magnitude speed increase on a
small dataset.



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Re: WHERE order

От
Tom Lane
Дата:
Rod Taylor <rbt@rbt.ca> writes:
> I would think that a simple optimization would be to push off evaluation
> of a subplan whenever possible by re-arranging AND statements.

Thought we did that already ... [ checks code ] ... hmph, it looks like
this is done correctly for quals attached to a scan node, but not for
quals attached to a join node.  Oops.
        regards, tom lane