migration.rb

class CreateGroupsAddressJoinTable < ActiveRecord::Migration
  def change
    create_join_table(:groups, :addresses, 'group_locations') do |t|
      # t.index [:group_id, :address_id]
      t.index :address_id
      t.index :group_id
      t.integer :address_id
      t.integer :group_id

    end
  end
end