Re: ERROR: failed to apply nullingrels to a non-Var

On Mon, Oct 12, 2026 at 10:18 AM Richard Guo <guofenglinux(at)gmail(dot)com> wrote:
> It seems to me that we should check required_relids instead here.
>
> - if (!bms_overlap(rinfo->clause_relids, rel->nulling_relids))
> + if (!bms_overlap(rinfo->required_relids, rel->nulling_relids))
>
> Or, maybe an alternative is to skip quals whose clause_relids overlap
> the rel's lateral_referencers, as join_clause_is_movable_to() does,
> but checking required_relids seems simpler to me.

After a million times of back and forth, I've decided to go with the
lateral_referencers fix, as it is easier to prove correct. Any
reference to the parent rel hidden inside a PHV evaluated elsewhere is
a lateral reference, so such quals always have one of the parent rel's
lateral referencers in their clause_relids. Skipping them is
harmless. Enforcing one at a scan of the parent rel would require
parameterizing the scan by a rel that itself depends on the parent
rel, which is circular.

The required_relids check turned out to be insufficient.
make_outerjoininfo() can't see PHV-hidden references either, so
required_relids may lack the nulling outer join. (And I think this is
another latent bug that we need to fix too.)

I've pushed the fix and back-patched it to v16.

- Richard