tab/db/migrate/20170123151219_rolify_create_roles.rb

class RolifyCreateRoles < ActiveRecord::Migration[5.0]
  def change
    create_table(:roles) do |t|
      t.string :name
      t.references :resource, polymorphic: true

      t.timestamps
    end

    create_table(:clients_roles, id: false) do |t|
      t.references :client
      t.references :role
    end

    add_index(:roles, :name)
    add_index(:roles, [ :name, :resource_type, :resource_id ])
    add_index(:clients_roles, [ :client_id, :role_id ])
  end
end