rails has_many至少有一个孩子有价值

Let say I have a Group of Users and User has a enum, which described it's mood.

假设我有一组用户,用户有一个枚举,描述了它的情绪。

class Group < AR::Base
  has_many :users

class User < AR::Base
  belongs_to :group
  enum mood: %i(good bad ugly)

How can I find all groups, where at least one User has the good mood?

我怎样才能找到所有团体,其中至少有一个用户心情愉快?

Which index should I add for optimizing this query?

我应该添加哪个索引来优化此查询?

1 个解决方案

#1

You can use joins method.

您可以使用连接方法。

Group.joins(:users).where("users.mood = ?", User.moods[:good])

You can add this into your migration

您可以将其添加到迁移中

add_index :users, :group_id