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Re: Inefficient query plan for SELECT ... EXCEPT ...

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On Tue, Oct 31, 2023 at 3:41 PM Dimitrios Apostolou <jimis@xxxxxxx> wrote:

Is this worth a bug report? I can file one if the issue is not known.
Or am I misunderstanding the implications of the SELECT-EXCEPT query?

In the meantime I have replaced the query with a LEFT OUTER JOIN which
performs much better,

I'd expect a NOT EXISTS query would also perform well and more accurately reflect what you seem to be wanting here.

I could see maybe optimizing away the second independent query if the first produces zero rows but it also doesn't seem like that productive an optimization to attempt.

David J.

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