mysql - Rails ActiveRecord 删除记录，一次删除一条关联记录

Question

这是一个示例...我有一个引用首选项的用户表。首选项表有一个 user_id。当我删除用户时，我想同时删除首选项表中的记录。但是，在模型中使用 belongs_to 和 has_many 关联方法，我在数据库上获得了此事件:

  preference Load (0.4ms)  SELECT `preferences`.* FROM `preferences` WHERE `preferences`.`user_id` = 2
  SQL (1.3ms)  DELETE FROM `preferences` WHERE `preferences`.`id` = 2
  SQL (0.2ms)  DELETE FROM `preferences` WHERE `preferences`.`id` = 6
  SQL (0.1ms)  DELETE FROM `preferences` WHERE `preferences`.`id` = 16
  SQL (0.2ms)  DELETE FROM `preferences` WHERE `preferences`.`id` = 28
  SQL (0.2ms)  DELETE FROM `preferences` WHERE `preferences`.`id` = 34
  SQL (0.1ms)  DELETE FROM `preferences` WHERE `preferences`.`id` = 44
  userAccount Load (0.3ms)  SELECT `user_accounts`.* FROM `user_accounts` WHERE `user_accounts`.`user_id` = 2
  SQL (0.2ms)  DELETE FROM `user_accounts` WHERE `user_accounts`.`id` = 2

是否有正确的方法可以使用从首选项中删除WHERE user_id = xxxx来删除记录？我想这样做，因为如果首选项有数百万行，可能是一个很长的查询。

# User model
has_many :preferences, dependent: :destroy

# Preferences model
belongs_to :user

我可以覆盖 destroy 方法，但我想看看是否有更优雅的方法来做到这一点......

Answer 1

你可以dependent: :delete_all选项，而不是dependent: :destroy:

has_many :preferences, dependent: :delete_all

这将执行从 user_id = {user_id} 的首选项中删除。