Tree-sitter: Emit empty_location relation to avoid scan

[hvitved]

Makes a difference on really large DBs, where scanning the full locations_default relation can be expensive:

[2024-05-24 08:14:11] Evaluated non-recursive predicate locations_default_234501#join_rhs@25a852j3 in 1551288ms (size: 1803722310).
Evaluated relational algebra for predicate locations_default_234501#join_rhs@25a852j3 with tuple counts:
        1803722310  ~0%    {6} r1 = SCAN locations_default OUTPUT In.2, In.3, In.4, In.5, In.0, In.1
                           return r1

[aibaars]

Looks good to me, although it feels a little strange that this would be needed. Wasn't there a way to improve this at the QL level?

[hvitved]

Wasn't there a way to improve this at the QL level?

I don't think there is, as any join on the empty file, needed to get to the empty location, would have to reorder the columns of locations_default.