Re: Convert NOT IN sublinks to anti-joins when safe

On Sun, Mar 8, 2026 at 5:16 PM Richard Guo <guofenglinux(at)gmail(dot)com> wrote:
> Attached is an updated version of the patch that replaces foreach with
> foreach_ptr or foreach_node accordingly. Nothing else has changed.
>
> I plan to do one more round of self-review on this. Unless there are
> any further thoughts or concerns, I'm hoping to commit this in a week
> or two. Please let me know if anyone spots anything else I might have
> missed.

I just finished a final self-review and noticed a subtle issue in
query_outputs_are_not_nullable(). When preparing a target expression
for the non-nullability check, the previous code flattened join
aliases Vars before grouping Vars. However, because the parser
processes FROM/JOIN clauses before the GROUP BY clause, a grouping Var
can actually wrap a join alias Var, not the reverse. So we should
flatten grouping Vars first.

Attached is an updated patch that fixes that issue. I plan to commit
this in a week or two, barring any objections.

- Richard