create_table :makes do |t|
      t.string  :name
    end

    create_table :models do |t|
      t.string  :name
      # stores the class_name of model if it exists (eg C-Class, 3 Series etc....)
      t.string :class_name
      # tracks number of this model that are actually on the market
      t.column :on_market_count, :integer, :default => 0
      # tracks the number of make model searches done for for this make/model
      t.integer :search_count, :default => 0
    end

    # for many-to-many reference
    create_table :models_makes,  :id => false do |column|
      column.integer :model_id,  :null => false
      column.integer :make_id,   :null => false
    end


    # add indexes
    add_index :makes,  :name
    add_index :models, :name
    add_index :models_makes, :model_id
    add_index :models_makes, :make_id