Re: creating of temporary table takes very long

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От Tom Lane
Тема Re: creating of temporary table takes very long
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Msg-id 19622.1145400512@sss.pgh.pa.us
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Ответ на Re: creating of temporary table takes very long  ("Jim C. Nasby" <jnasby@pervasive.com>)
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"Jim C. Nasby" <jnasby@pervasive.com> writes:
> You might try rewriting the coalesces into a row comparison...
> WHERE row($4, $5, ...) IS NOT DISTINCT FROM row(interface_id, source_id, ...)

That would be notationally nicer, but no help performance-wise; I'm
fairly sure that IS DISTINCT doesn't get optimized in any fashion
whatsoever :-(

What might be worth trying is functional indexes on the COALESCE(foo,0)
expressions.  Or if possible, consider revising your data schema to
avoid using NULLs in a way that requires assuming that NULL = NULL.

            regards, tom lane

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