Function install_lifted_mfp

fn install_lifted_mfp(
    new_join: &mut MirRelationExpr,
    mfp: MapFilterProject,
) -> Result<(), TransformError>

This function continues the surgery that implement_arrangements started.

(In theory, this function could be merged into implement_arrangements, but it would be a bit painful, because we need to access the join’s implementation after implement_arrangements, which would be somewhat convoluted after what install_lifted_mfp does.)

The given MFP should be the merged MFP from all the lifted inputs MFPs.

install_lifted_mfp mutates the given join expression as follows:

• Puts the given MFP on top of the Join.
• Attends to equivalences, which was invalidated by implement_arrangements if it refers to a column that was permuted or created by the given MFP.
• Canonicalizes scalar expressions in maps and filters with respect to the join equivalences. See inline comment for more details.