pub trait DataOrd<Rhs> { }
Marker trait to determine whether values can be compared. Unlike PartialOrd, handles Option, which we need for nullable types.
PartialOrd
Option
impl<T> DataOrd<T> for Option<T> where T: PartialOrd<T> + FieldType,
impl<T> DataOrd<T> for T where T: PartialOrd<T> + FieldType,