Ruby Sequel: Multiple Unique foreign key sample

sequel_multiple_unique_key.rb

class DailyFriendList < Sequel::Model                                                                    
  many_to_one :player                                                                                    
  set_schema do                                                                                          
    primary_key :id                                                                                      
    foreign_key :player_id, :players                                                                     
    foreign_key :friend_id, :players                                                                     
    date :date                                                                                           
    index [:player_id, :friend_id, :date], :unique => true                                               
  end                                                                                                    
                                                                                                         
  def self.create_friends(player_id, date_string, friend_id_list)                                        
    date = Time.parse(date_string)                                                                       
    friend_id_list.each do |friend_id|                                                                   
      self.create(:player_id => player_id,                                                               
                  :date => date,                                                                         
                  :friend_id => friend_id)                                                               
    end                                                                                                  
  end                                                                                                    
end