Re: Odd statistics behaviour in 7.2 - Mailing list pgsql-hackers

From Tom Lane
Subject Re: Odd statistics behaviour in 7.2
Date
Msg-id 21370.1013891666@sss.pgh.pa.us
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In response to Re: Odd statistics behaviour in 7.2  (Bruno Wolff III <bruno@wolff.to>)
List pgsql-hackers
Bruno Wolff III <bruno@wolff.to> writes:
> Tom Lane <tgl@sss.pgh.pa.us> wrote:
>> A lot of the other equations I looked at depend on
>> series like (1 - n/N)**i which are going to be really nasty when n/N
>> is tiny.

> You can work with the above for n << N by using power series. For n << N,
> (1 - n/N)**i ~= 1 - in/N.

Yeah, but the pain-in-the-neck aspect comes from the fact that n/N isn't
necessarily tiny --- it could approach 1.  So you'd need code smart
enough to handle both cases with accuracy.

We could probably do this if it proves necessary, but I'd like to stick
to simpler equations if at all possible.
        regards, tom lane


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