remove duplicates from activerecord

company.rb

  def self.dedupe
    # find all models and group them on keys which should be common
    grouped = all.group_by{|model| [model.title,model.info,model.address,model.phone] }
    grouped.values.each do |duplicates|
      # the first one we want to keep right?
      first_one = duplicates.shift # or pop for last one
      # if there are any more left, they are duplicates
      # so delete all of them
      duplicates.each{|double| double.destroy} # duplicates can now be destroyed
    end
  end

how do I club order_by to the above group_by?