Rails migration create table with bigint id

gistfile1.rb

class CreateBooks < ActiveRecord::Migration
  def up
    create_table :books do |t|
      t.string  :name
      t.integer :price

      t.timestamps
    end
    execute 'ALTER TABLE books MODIFY id bigint(20) DEFAULT NULL auto_increment NOT NULL'
  end

  def down
    drop_table :books
  end
end