Jim Finnerty writes:
> It's related, but what I was referring to applies even to the uncorrelated
> case: suppose you have something like:
> select x, sum(z)
> from t
> where
> x > 5 and y in ('a', 'b', 'c')
> group by x;
> let's say that 'a', 'b', and 'c' are not frequent values of y, so t
Jim Finnerty 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 predi
Edmund Horner writes:
> I added some code to selfuncs.c to estimate the selectivity of CTID,
> including nullness, in my ongoing attempt to add TID range scans [1]. And
> as Tom pointed out [2], no system attribute can be null, so we might as
> well handle them all.
> That's what the attached pat
