Ruby：迁移中的 add_reference 会引发错误：表没有

Question

我有这个迁移：

class AddNotificationSettingToHistoricals < ActiveRecord::Migration[6.1]
  def change
    unless foreign_key_exists?(:sms_historicals, column: :notification_setting_id)
      add_reference :sms_historicals, :notification_setting, foreign_key: true
    end
    unless foreign_key_exists?(:email_historicals, column: :notification_setting_id)
      add_reference :email_historicals, :notification_setting, foreign_key: true
    end
  end
end

但是当我运行它时，它会抛出此错误：

Table 'email_historicals' has no foreign key for notification_settings

我不明白的是我在迁移中有这些：

unless foreign_key_exists?(:email_historicals, column: :notification_setting_id)

这确实会抛出错误..所以是的，没有外键，这就是我尝试添加它的原因..是的，我不确定为什么要这样做..有什么想法吗？

Answer 1

基于 https://gitlab.com/gitlab-org/gitlab/-/issues/394760 如果在 postgres_foreign_keys 具有正确的列之前在迁移中运行，看起来

foreign_key_exists?

可能会引发错误。他们建议的解决方法是使用

column_exists?

代替

class AddNotificationSettingToHistoricals < ActiveRecord::Migration[6.1]
  def change
    unless column_exists?(:sms_historicals, :notification_setting_id)
      add_reference :sms_historicals, :notification_setting, foreign_key: true
    end
    unless column_exists?(:email_historicals, :notification_setting_id)
      add_reference :email_historicals, :notification_setting, foreign_key: true
    end
  end
end