Rails迁移-暂时忽略外键约束？

Question

class AddUuidToProjects < ActiveRecord::Migration[5.0]
  def up
    add_column :projects, :uuid, :string, limit:36, null: false, first: true
    add_column :projects, :old_id, :integer

    Project.all.each do |p|
      p.update!(old_id: p.id)
    end
    change_table :projects do |t|
      t.remove :id
      t.rename :uuid, :id
    end
    execute "ALTER TABLE projects ADD PRIMARY KEY (id);"

    Project.all.each do |p|
      # has_one image
      Image.find(p.old_id).update!(project: p) 
      # has_many stories
      Story.where(project_id: p.old_id).each do |s|
        s.update!(project: p)
      end
    end
  end
  ...
end

Mysql2::Error: Cannot drop column 'id': needed in a foreign key constraint 'fk_rails_be41fd4bb7' of table 'db_dev.stories': ALTER TABLE `projects` DROP `id`

问题是，如果整个迁移运行，那么我将用另一列替换id列，并修复外键。那么，有什么方法可以忽略迁移的约束呢？

Answer 1

ActiveRecord::base.connection.disable_referential_integrity(Github)。至少需要Rails4.2。

附言。

我发现上面的代码很容易出错。对我来说，主要原因是缺乏对如此重要任务的测试。“ThoughtBot”中有一篇关于将数据迁移与结构迁移混合的其他问题的文章。