Re: Assert failure in get_baserel_parampathinfo with lateral UNION ALL

HI Richard

I think the change to derive `clause_relids` from the child EMs makes
> sense, especially for the lateral-reference case described in the patch.
> One thing I may be missing, though: after replacing
> `rinfo->clause_relids`, should we also update `rinfo->num_base_rels`?
> `make_restrictinfo()` computes `num_base_rels` from the original
> `clause_relids`, but this patch subsequently replaces `clause_relids` for
> child clauses.
> In cases involving lateral references and nulling outer joins, the two
> sets can be different, so `num_base_rels` could potentially become stale.
> Would it be safer to recompute it from the new `clause_relids` here, using
> the same definition as in `make_restrictinfo()`?
> I am not sure whether there is an invariant elsewhere that makes
> `num_base_rels` unaffected in these cases. I
> t might also be useful to add a regression case specifically covering this
> metadata, in addition to the existing plan/execution coverage.
>

Thanks