Re: remove_useless_joins vs. bug #19560 - Mailing list pgsql-hackers

On Wed, Sep 16, 2026 at 1:56 PM Richard Guo <guofenglinux@gmail.com> wrote:
> I think we have to insist that the preprocessing happens after join
> alias expansion, which is what my v2 patch in [1] did.  But that patch
> was not complete: as I explained in [2], it doesn't handle copies that
> were pushed into a SubLink's subselect.  I think we can cover those by
> also running the preprocessing in preprocess_expression, right before
> SS_process_sublinks.  That way each upper-level PHV is preprocessed
> exactly once, at the level it belongs to, and always after join alias
> expansion.
>
> Hence, the attached fix.

I've pushed this patch and back-patched it to v16.

- Richard