Re: *very* inefficient choice made by the planner (regarding

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От Tom Lane
Тема Re: *very* inefficient choice made by the planner (regarding
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Msg-id 25304.1086883145@sss.pgh.pa.us
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Ответ на Re: *very* inefficient choice made by the planner (regarding  (Jean-Luc Lachance <jllachan@sympatico.ca>)
Ответы Re: *very* inefficient choice made by the planner (regarding  (Jean-Luc Lachance <jllachan@sympatico.ca>)
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Jean-Luc Lachance <jllachan@sympatico.ca> writes:
> If the two statments are functionally equivalent, why can't PG rewrite
> the "NOT IN" version into the more efficient "NOT EXISTS"?

They're not equivalent.  In particular, the behavior in the presence of
NULLs is quite different.

            regards, tom lane

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