code: def delete(cv)
        @executor.transact do |dbh|
          sth = dbh.prepare(DELETE_STMT)
          delete_recursive(cv, sth)
          sth.finish
        end
      end
docs: Deletes the given ControlledValue record in the database. Recursively deletes the
   transitive closure of children as well.
  
   @param [ControlledValue] cv the controlled value to delete