Re: Correlation in cost_index()

On Fri, 08 Aug 2003 18:25:41 -0400, Tom Lane <tgl@sss.pgh.pa.us>
wrote:
>  Two examples: [...]

One more example:X    Y
A    Aa    BA    Cb    AB    Bb    CC    Ac    BC    C

Correlation for column X is something less than 1.0, OTOH correlation
for an index on upper(X) is 1.0.

>I don't really see
>a way to do this without actually examining the multi-column ordering
>relationship during ANALYZE.

So did we reach consensus to add a TODO item?
* Compute index correlation on CREATE INDEX and ANALYZE,  use it for index scan cost estimation

ServusManfred