Function mz_transform::threshold_elision::is_superset_of

pub fn is_superset_of(lhs: &MirRelationExpr, rhs: &MirRelationExpr) -> bool

Returns true iff rhs is always a subset of lhs.

This method is a conservative approximation and is known to miss not-hard cases.

We iteratively descend rhs through a few operators, looking for lhs. In addition, we descend simultaneously through lhs and rhs if the root node on both sides is identical.