On Wed, Aug 3, 2016 at 4:58 AM, Tomas Vondra
<tomas.vondra@2ndquadrant.com> wrote:
> 2) combining multiple statistics
>
> I think the ability to combine multivariate statistics (covering different
> subsets of conditions) is important and useful, but I'm starting to think
> that the current implementation may not be the correct one (which is why I
> haven't written the SGML docs about this part of the patch series yet).
While researching this topic a few years ago I came across a paper on
this exact topic called "Consistently Estimating the Selectivity of
Conjuncts of Predicates" [1]. While effective it seems to be quite
heavy-weight, so would probably need support for tiered optimization.
[1] https://courses.cs.washington.edu/courses/cse544/11wi/papers/markl-vldb-2005.pdf
Regards,
Ants Aasma