Ruby on rails ActiveRecord和查询

我有三种模式：用户模式、对话模式和对话模式

class User < ApplicationRecord
  has_many :conversation_users, dependent: :destroy
  has_many :conversations, through: :conversation_users
end

我的问题

我只想找到第一个用户和第二个用户的对话。 如果我执行以下查询，Active Record仍将显示对话，因为它正在执行OR子句，但我需要AND。 正确的结果应该显示一个空数组，因为没有与User.first和User.third的对话

期望值

应找到与User.first和User.second的对话 不应找到与User.first和User.third的对话 我第一次尝试了这个查询，但是它返回了一个空数组

Conversation.joins(:conversation_users).where(conversation_users: {user_id: User.first.id}).where(conversation_users: {user_id: User.second.id})

  User Load (3.8ms)  SELECT "users".* FROM "users" ORDER BY "users"."created_at" ASC LIMIT $1  [["LIMIT", 1]]
  User Load (4.0ms)  SELECT "users".* FROM "users" ORDER BY "users"."created_at" ASC LIMIT $1 OFFSET $2  [["LIMIT", 1], ["OFFSET", 1]]
  Conversation Load (3.3ms)  SELECT "conversations".* FROM "conversations" INNER JOIN "conversation_users" ON "conversation_users"."conversation_id" = "conversations"."id" WHERE "conversation_users"."user_id" = $1 AND "conversation_users"."user_id" = $2 LIMIT $3  [["user_id", "274d2f54-2418-4dec-a696-a5f62196ee85"], ["user_id", "44a0c35a-b5c1-4bb6-a8a3-30ae3d4b3345"], ["LIMIT", 11]]
=> #<ActiveRecord::Relation []>

您可以使用和条件执行查询，如下所示

Conversation.joins(:conversation_users).where(conversation_users: {user_id: User.first.id}).where(conversation_users: {user_id: User.second.id})

这将导致以下SQL查询：

SELECT "conversations".* FROM "conversations" 
INNER JOIN "user_conversations" ON "user_conversations"."conversation_id" = "conversations"."id" 
WHERE 
  (EXISTS(SELECT * FROM user_conversations uc WHERE uc.conversation_id = conversations.id AND uc.user_id = 1))
  AND 
  (EXISTS(SELECT * FROM user_conversations uc WHERE uc.conversation_id = conversations.id AND uc.user_id = 2)) 
GROUP BY "conversations"."id"
HAVING (count(*) = 2) 
LIMIT $1

---

我编辑了我的问题以便更清楚。使用您的解决方案，我无法找到与User.first和User.second的对话，它返回的是一个空数组

Conversation.joins(:conversation_users).where(conversation_users: {user_id: [User.first.id, User.third.id]})

  User Load (3.3ms)  SELECT "users".* FROM "users" ORDER BY "users"."created_at" ASC LIMIT $1  [["LIMIT", 1]]
  User Load (2.5ms)  SELECT "users".* FROM "users" ORDER BY "users"."created_at" ASC LIMIT $1 OFFSET $2  [["LIMIT", 1], ["OFFSET", 2]]
  Conversation Load (3.9ms)  SELECT "conversations".* FROM "conversations" INNER JOIN "conversation_users" ON "conversation_users"."conversation_id" = "conversations"."id" WHERE "conversation_users"."user_id" IN ($1, $2) LIMIT $3  [["user_id", "274d2f54-2418-4dec-a696-a5f62196ee85"], ["user_id", "0ef2f797-3518-4096-951b-1837ca28e4e4"], ["LIMIT", 11]]
=> #<ActiveRecord::Relation [#<Conversation id: "35556705-a162-4ee4-9776-963ae87bcfa8", created_at: "2020-04-20 09:34:05", updated_at: "2020-04-20 09:34:05">]>

Conversation.joins(:conversation_users).where(conversation_users: {user_id: User.first.id}).where(conversation_users: {user_id: User.second.id})

  User Load (3.8ms)  SELECT "users".* FROM "users" ORDER BY "users"."created_at" ASC LIMIT $1  [["LIMIT", 1]]
  User Load (4.0ms)  SELECT "users".* FROM "users" ORDER BY "users"."created_at" ASC LIMIT $1 OFFSET $2  [["LIMIT", 1], ["OFFSET", 1]]
  Conversation Load (3.3ms)  SELECT "conversations".* FROM "conversations" INNER JOIN "conversation_users" ON "conversation_users"."conversation_id" = "conversations"."id" WHERE "conversation_users"."user_id" = $1 AND "conversation_users"."user_id" = $2 LIMIT $3  [["user_id", "274d2f54-2418-4dec-a696-a5f62196ee85"], ["user_id", "44a0c35a-b5c1-4bb6-a8a3-30ae3d4b3345"], ["LIMIT", 11]]
=> #<ActiveRecord::Relation []>

Conversation.joins(:conversation_users).where(conversation_users: {user_id: User.first.id}).where(conversation_users: {user_id: User.second.id})

class Conversation < ApplicationRecord
  has_many :user_conversations
  has_many :users, through: :user_conversations

  def self.between(*users)
    users.map do |u|
      where("EXISTS(SELECT * FROM user_conversations uc WHERE uc.conversation_id = conversations.id AND uc.user_id = ?)", u)
    end.reduce(&:merge)
      .joins(:user_conversations)
      .group(:id)
      .having('count(*) = ?', users.length)
  end
end

Conversation.between(User.first, User.second)
Conversation.between(1,2,3)
Conversation.between(*User.all) # splat it like a pro

SELECT "conversations".* FROM "conversations" 
INNER JOIN "user_conversations" ON "user_conversations"."conversation_id" = "conversations"."id" 
WHERE 
  (EXISTS(SELECT * FROM user_conversations uc WHERE uc.conversation_id = conversations.id AND uc.user_id = 1))
  AND 
  (EXISTS(SELECT * FROM user_conversations uc WHERE uc.conversation_id = conversations.id AND uc.user_id = 2)) 
GROUP BY "conversations"."id"
HAVING (count(*) = 2) 
LIMIT $1