# This migration file creates the many-to-many relationship between
# actors and movies.  In particular, it creates the join table named
# actors_movies
#
# IMPORTANT: Rails expects that the join table has the model names presented
# in alphabetical order (e.g. actors come before movies)
#
# The skeleton of this migration file was created with this command
#    ruby script/generate migration CreateActorsMovies
#
# The options for this connecting table indicate that "id" will not be
# present and that actor_id and movie_id cannot have null values.
#
# This migration file also sets up an index for efficient look-up.
#
# To complete the relationship for the models, the following need to be added:
#    To app/models/actor.rb
#         has_and_belongs_to_many :movies
#    To app/models/movie.rb
#         has_and_belongs_to_many :actors
#
# A similar example is covered in Learning Rails, pp. 162 - 165

class CreateActorsMovies < ActiveRecord::Migration
  def self.up
    create_table :actors_movies, :id => false do |t|
      t.integer :actor_id, :null => false
      t.integer :movie_id, :null => false
    end
    
    add_index :actors_movies, [:actor_id, :movie_id], :unique => true
  end

  def self.down
    remove_index :actors_movies, :column => [:actor_id, :movie_id]
    drop_table :actors_movies
  end
end