Function bind_join_sides 

pub fn bind_join_sides<'a>(
    left: &RowSchema,
    right: &RowSchema,
    lhs: &'a ScalarExpr,
    rhs: &'a ScalarExpr,
) -> Option<(Cow<'a, ScalarExpr>, Cow<'a, ScalarExpr>)>

Rebase selected right-input positions for independent key evaluation, borrowing expressions whose coordinates already match their own input.