Re: Correlation in cost_index() - Mailing list pgsql-hackers

From Manfred Koizar
Subject Re: Correlation in cost_index()
Date
Msg-id kjvopusi65nsige1l7le9tmf6ds8acd6ne@4ax.com
Whole thread Raw
In response to Re: Correlation in cost_index()  ("scott.marlowe" <scott.marlowe@ihs.com>)
Responses Re: Correlation in cost_index()  (Tom Lane <tgl@sss.pgh.pa.us>)
List pgsql-hackers
On Thu, 3 Oct 2002 10:59:54 -0600 (MDT), "scott.marlowe"
<scott.marlowe@ihs.com> wrote:
>>are multicolunm indices involved in your estimator problems?
>
>No.  Although I use them a fair bit, none of the problems I've encountered 
>so far have involved them.  But I'd be willing to setup some test indexes 
>and get some numbers on them.

Never mind!  I just stumbled over those lines in selfuncs.c where
indexCorrelation is calculated by dividing the correlation of the
first index column by the number of index columns.

I have a use case here where this clearly is not the right choice and
was hoping to find some examples that help me investigate whether my
case is somewhat uncommon ...

ServusManfred


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