Kevin Grittner wrote:
> Shaun Thomas <sthomas@xxxxxxxxx> wrote:
>
> > how difficult would it be to add that syntax to the JOIN
> > statement, for example?
>
> Something like this syntax?:
>
> JOIN WITH (correlation_factor=0.3)
>
> Where 1.0 might mean that for each value on the left there was only
> one distinct value on the right, and 0.0 would mean that they were
> entirely independent? (Just as an off-the-cuff example -- I'm not
> at all sure that this makes sense, let alone is the best thing to
> specify. I'm trying to get at *syntax* here, not particular knobs.)
I am not excited about the idea of putting these correlations in
queries. What would be more intesting would be for analyze to build a
correlation coeffficent matrix showing how columns are correlated:
a b c
a 1 .4 0
b .1 1 -.3
c .2 .3 1
and those correlations could be used to weigh how the single-column
statistics should be combined.
--
Bruce Momjian <bruce@xxxxxxxxxx> http://momjian.us
EnterpriseDB http://enterprisedb.com
+ It's impossible for everything to be true. +
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