通过 Rails 中的迁移添加自动增量

如何向名为的列添加自动增量属性user_number在我的桌子上users通过 Rails 迁移。

我已经有一个 id 字段，它是它的主键，并且它是一个自动增量字段。我正在尝试创建一个新的自动增量字段而不删除此 id 字段..

class CreateSimpleModels < ActiveRecord::Migration
  def self.up
    create_table :simple_models do |t|
      t.string :name
      t.integer :user_number
      t.timestamps
    end
    execute "CREATE SEQUENCE simple_models_user_number_seq OWNED BY
simple_models.user_number INCREMENT BY 1 START WITH 1"
  end

  def self.down
    drop_table :simple_models
    execute "DELETE SEQUENCE simple_models_user_number_seq"
  end
end