On Wed, Dec 25, 2024 at 11:34 AM Andrei Lepikhov <lepihov@gmail.com> wrote:
> I have a couple of notes.
> 1. The nulling_relids provides us sensible information about possible
> nulls inside the input. We are not using it to estimate the number of
> such nulls for now. Does Your idea consist of obtaining 'clear'
> statistics and reusing nulling_relids knowledge somewhere later?
Are you referring to the nullfrac estimates? A RelOptInfo's
nulling_relids records all above outer joins that can null this rel.
However, I cannot see how it helps with nullfrac.
> 2. It is ok for Vars. But what about expressions? We use equal() in
> distinct, MCV and dependencies modules. Do we need to remove nulls
> before using extended statistics as a general rule?
AFAIU, the expressions in extended statistics are not decorated with
any nullingrels bits, are they?
Thanks
Richard
