Re: Worse perfomance on 8.2.0 than on 7.4.14

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От Tom Lane
Тема Re: Worse perfomance on 8.2.0 than on 7.4.14
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Msg-id 3425.1167750444@sss.pgh.pa.us
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Ответ на Re: Worse perfomance on 8.2.0 than on 7.4.14  (Rolf Østvik <rolfostvik@yahoo.no>)
Ответы Re: Worse perfomance on 8.2.0 than on 7.4.14  (Rolf Østvik <rolfostvik@yahoo.no>)
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=?iso-8859-1?q?Rolf=20=D8stvik?= <rolfostvik@yahoo.no> writes:
> If you (Tom) still want me to do the following steps
> then please tell me.

Please --- I'm still curious why the estimated cost changed so much from
7.4 to 8.2.  I can believe a marginal change in cost leading to a plan
switch, but comparing the total-cost numbers shows that 8.2 must think
that indexscan is a whole lot more expensive than 7.4 did, which seems
odd.  For the most part 8.2 ought to think nestloop-with-inner-indexscan
is cheaper than 7.4 did, because we now account for caching effects across
repeated iterations of the inner scan.

            regards, tom lane

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