Question

将我的Rails 4.2应用程序迁移到Rails 5后，当我尝试从新数据库迁移时出现以下错误

表＆＃39>目标＆＃39;没有用于development_plan的外键

以下是重要的迁移：

使用add_reference

创建foreign_key

class AddDevelopmentPlanToObjectives < ActiveRecord::Migration
  def change
    add_reference :objectives, :development_plan, index: true, foreign_key: true
  end
end

删除外键（生成错误）

class DropDevelopmentPlans < ActiveRecord::Migration
  def change
    Objective.all.each do |objective|
      company = objective.owner.company
      company.cycles.create name: '4Q 2015', begin_at: Date.today, end_at: 1.year.from_now, current: true unless company.current_cycle
      company.reload
      objective.update cycle: company.current_cycle
    end
    remove_foreign_key :objectives, :development_plan
    remove_reference :objectives, :development_plan, index: true
    drop_table :development_plans
  end
end

remove_foreign_key :objectives, :development_plan

有人有这个问题吗？这也发生在其他类似的迁移中......

Answer 1

参考这篇文章：https://blog.bigbinary.com/2016/03/01/migrations-are-versioned-in-rails-5.html

Rails 5为迁移类添加了一个版本：

在Rails 5.0中生成的迁移：

class CreateTasks < ActiveRecord::Migration[5.0]
 ...
end

如果您没有，它将尝试向我们提供兼容性层。虽然该兼容层针对的是Rails 4.2，并且根据该文章它应该默认为什么，但我会尝试将您的迁移更改为所有用途：

class AddDevelopmentPlanToObjectives < ActiveRecord::Migration[4.2]
  ....

看看是否有帮助。如果不是，我会更改您的迁移以适应v5.0概述的更改

class AddDevelopmentPlanToObjectives < ActiveRecord::Migration[5.0]
  def change
    add_reference :objectives, :development_plan, foreign_key: true
  end
end

class DropDevelopmentPlans < ActiveRecord::Migration[5.0]
  def change
    Objective.all.each do |objective|
      company = objective.owner.company
      company.cycles.create name: '4Q 2015', begin_at: Date.today, end_at: 1.year.from_now, current: true unless company.current_cycle
      company.reload
      objective.update cycle: company.current_cycle
    end
    remove_foreign_key :objectives, :development_plan
    remove_reference :objectives, :development_plan
    drop_table :development_plans
  end
end

Answer 2

我相信 to_table 应该以复数形式倾斜：

remove_foreign_key :objectives, to_table: :development_plans

请参阅rails api docs。

Rails5迁移：表没有外键

2 个答案: