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

HI Richard

> Thanks for reporting this and tracking it down to lateral PHVs.
>
> Between the two approaches you mentioned, I'm personally more inclined
> towards your second thought (checking lateral_referencers).
>
> My slight concern with switching to required_relids is that
> required_relids and nulling_relids serve slightly different purposes
> conceptually. While checking required_relids happens to catch the issue
> here, I wonder if that might be an indirect effect of how PHV's ph_eval_at
> tracks outer joins. For instance, if s were involved in an inner join
> instead of a left join, rel->nulling_relids would be empty, but we
> probably still wouldn't want to push down a qual that references s's
> lateral referencers into the child relations.
>
> In that sense, checking rel->lateral_referencers seems to capture the root
> of the problem more naturally: the qual references something (ss) that
> topologically depends on s, so it shouldn't be pushed down to s's child
> relations in the first place. That also aligns very well with the
> reasoning already used in join_clause_is_movable_to().
>
> So perhaps something like this would be a bit more robust:
>
> diff
> - if (!bms_overlap(rinfo->clause_relids, rel->nulling_relids))
> + if (!bms_overlap(rinfo->clause_relids, rel->nulling_relids) &&
> + !bms_overlap(rinfo->clause_relids, rel->lateral_referencers))
>
> What do you think?
>
>
>
Regards