Re: Performance

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От Robert Haas
Тема Re: Performance
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Msg-id 11589CE9-B860-4024-BCDF-88FBE00FB9BC@gmail.com
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Ответ на Re: Performance  (Tomas Vondra <tv@fuzzy.cz>)
Ответы Re: Performance  (Tomas Vondra <tv@fuzzy.cz>)
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On Apr 13, 2011, at 6:19 PM, Tomas Vondra <tv@fuzzy.cz> wrote:
> Yes, I've had some lectures on non-linear programming so I'm aware that
> this won't work if the cost function has multiple extremes (walleys /
> hills etc.) but I somehow suppose that's not the case of cost estimates.

I think that supposition might turn out to be incorrect, though.  Probably what will happen on simple queries is that a
smallchange will make no difference, and a large enough change will cause a plan change.  On complex queries it will
approachcontinuous variation but why shouldn't there be local minima? 

...Robert

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