Re: Very ineffective plan with merge join

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От Tom Lane
Тема Re: Very ineffective plan with merge join
Дата
Msg-id 25335.1271368858@sss.pgh.pa.us
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Ответ на Re: Very ineffective plan with merge join  ("Kevin Grittner" <Kevin.Grittner@wicourts.gov>)
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"Kevin Grittner" <Kevin.Grittner@wicourts.gov> writes:
> What's up with the sort of _accrged7200 (in the slower plan) taking
> in 3.5 million rows and putting out 1 row?  There's something there
> I'm not understanding.

It's under a merge join, so what probably happened is that the first
row from that side had a larger key than any row from the other side.
A mergejoin will never bother to look at the remaining rows in such
a case.
        regards, tom lane


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