Re: Removing const-false IS NULL quals and redundant IS NOT NULL quals

[Richard Guo]

On Wed, Dec 27, 2023 at 7:38 PM Andy Fan <zhihuifan1...@163.com> wrote:

> I also want to add notnullattnums for the UniqueKey stuff as well, by
> comparing your implementation with mine,  I found you didn't consider
> the NOT NULL generated by filter. After apply your patch:
>
> create table a(a int);
> explain (costs off) select * from a where a > 3 and a is null;
>              QUERY PLAN
> -------------------------------------
>  Seq Scan on a
>    Filter: ((a IS NULL) AND (a > 3))
> (2 rows)


The detection of self-inconsistent restrictions already exists in
planner.

# set constraint_exclusion to on;
SET
# explain (costs off) select * from a where a > 3 and a is null;
        QUERY PLAN
--------------------------
 Result
   One-Time Filter: false
(2 rows)

Thanks
Richard