Ruby 向现有模型添加单表继承（STI）

我目前有多个非常相似的表。我应该用STI来制作它们

TypeOne < ActiveRecord::Base
TypeTwo < ActiveRecord::Base
TypeThree < ActiveRecord::Base

TypeOne(id: integer, parent_id: integer, created_at: datetime, updated_at: datetime)
TypeTwo(id: integer, parent_id: integer, created_at: datetime, updated_at: datetime)
TypeThree(id: integer, parent_id: integer, created_at: datetime, updated_at: datetime)

我还运行了一次迁移，并在所有类型中添加了一个类型列

class AddTypeToTables < ActiveRecord::Migration
  def change
    add_column :type_ones, :type, :string
    add_column :type_twos, :type, :string
    add_column :type_threes, :type, :string
  end
end

我尝试将每个类更改为BaseModel的子类

TypeOne.last.becomes!(BaseModel)
#<BaseModel id: 4, parent_id: 1, created_at: "2015-05-08 18:39:09", updated_at: "2015-09-07 19:42:03">

BaseModel.all
=> []

TypeOne < BaseModel
TypeTwo < BaseModel
TypeThree < BaseModel

TypeOne

执行此操作时，我将失去与现有数据的连接，并且每个模型都显示为空

---

如何组合现有表？

您已经用PostgreSQL对其进行了标记，我将介绍如何执行我在评论中建议的操作，作为答案：

INSERT INTO base_model SELECT * FROM type_one ORDER BY id ASC;
INSERT INTO base_model SELECT * FROM type_two ORDER BY id ASC;
INSERT INTO base_model SELECT * FROM type_three ORDER BY id ASC;

为了在生产数据集上安全地执行此操作，请将SQL放在db/migrate中的迁移中（即，放在db/migrate/20150907185938_integrate_tables.rb这样的文件中），然后首先在本地数据库上测试它。这会让你非常接近：

class IntegrateTables < ActiveRecord::Migration
  def up
    execute "INSERT INTO base_model SELECT * FROM type_one ORDER BY id ASC;"
    execute "INSERT INTO base_model SELECT * FROM type_two ORDER BY id ASC;"
    execute "INSERT INTO base_model SELECT * FROM type_three ORDER BY id ASC;"
  end

  def down
    raise ActiveRecord::IrreversibleMigration, "It is unclear where original data stops and inserted data begins, can't migrate down"
  end
end

class IntegrateTables

---

如果此答案对您有效，请将其标记为已接受：）

是否有任何外键引用记录的id（例如键入\ one.id、键入\ two.id等）？如果不是，我建议从一个表中选择并插入到BaseModel的表中，这将更改ID，以便在正确设置主键的情况下不会发生冲突。然后使用继承结构，就像使用itSTI=单表继承一样。要按预期使用它，您需要将所有数据放在一个表中，这是有意义的，谢谢对于生产数据集，有什么干净的方法可以做到这一点吗？在下面的回答中添加了它

TypeOne < BaseModel
TypeTwo < BaseModel
TypeThree < BaseModel

INSERT INTO base_model SELECT * FROM type_one ORDER BY id ASC;
INSERT INTO base_model SELECT * FROM type_two ORDER BY id ASC;
INSERT INTO base_model SELECT * FROM type_three ORDER BY id ASC;

class IntegrateTables < ActiveRecord::Migration
  def up
    execute "INSERT INTO base_model SELECT * FROM type_one ORDER BY id ASC;"
    execute "INSERT INTO base_model SELECT * FROM type_two ORDER BY id ASC;"
    execute "INSERT INTO base_model SELECT * FROM type_three ORDER BY id ASC;"
  end

  def down
    raise ActiveRecord::IrreversibleMigration, "It is unclear where original data stops and inserted data begins, can't migrate down"
  end
end