Re: Use zero for nullness estimates of system attributes

Jim Finnerty <jfinnert@amazon.com> writes:
> Tom, there's an analogous issue of adjusting distinct values on a per-column
> basis based on the selectivity of other local predicates.  Several
> commercial RDBMS's make such adjustments in an effort to get better
> selectivity estimates when there are multiple local predicates.  Is this
> something that the PG community has considered and decided not to do because
> of the additional planning-time overhead that may be required, or just
> something that hasn't been discussed or tackled yet?

I think what you're talking about is the correlated-variables problem,
which we have made a start on with the "extended statistics" mechanism,
though certainly a lot remains to be done.

            regards, tom lane