Re: Anti join confusion - Mailing list pgsql-hackers

On Wed, Feb 26, 2025 at 7:09 PM Tender Wang <tndrwang@gmail.com> wrote:
> Recently, I found Greenplum implement pull-up NOT IN subquery. They have the below comments in their codes:
>
> We normalize NOT subqueries using the following axioms:
> *
> * val NOT IN (subq) =>  val <> ALL (subq)
>
> Richard, do you have an impression about this?

I vaguely recall that Greenplum converts NOT IN to some form of join
in certain cases, but I can't remember the details.

Thanks
Richard