class ActiveRecord::Relation::Merger

def merge_multi_values
  if other.reordering_value
    # override any order specified in the original relation
    relation.reorder!(*other.order_values)
  elsif other.order_values.any?
    # merge in order_values from relation
    relation.order!(*other.order_values)
  end
  extensions = other.extensions - relation.extensions
  relation.extending!(*extensions) if extensions.any?
end