消息传递应用程序的MongoDB聚合查询

我正在开发一个具有消息功能（聊天）的应用程序，我希望获得所有我拥有的用户或向我发送消息的用户，并按照最近通信的联系人到达顶部的顺序对所有这些用户进行分组。 并统计了我从另一个用户那里收到的、我还没有读过的所有信息

Mongo消息模型

const userChat = new Schema({
  senderUserId: {
    type: Schema.Types.ObjectId,
    ref: "User"
  },
  message: {
    type: String
  },
  room: {
    type: Array
  },
  files: {
    type: Array
  },
  read: {
    type: Boolean,
    default: false
  },
  receiverUserId: {
    type: Schema.Types.ObjectId,
    ref: "User"
  }
}, {
  timestamps: true
})

我的MongoDB聚合

const user = await UserChat.aggregate([{
  $match: {
    $and: [{
      $or: [{
          receiverUserId: req.user._id
        }, // User is in recepients
        {
          senderUserId: req.user._id
        }, // or the sender
      ],
    }, ],
  },
},
{
  $sort: {
    createdAt: -1,
  },
},
{
  // if the message is send by me then i group the "$receiverUserId"
  // if not that mean i am the receiver so i group the "$senderUserId"
  $group: {
    _id: {
      $cond: {
        if: {
          $eq: ["$senderUserId", req.user._id]
        },
        then: "$receiverUserId",
        else: "$senderUserId"
      }
    },
    count: {
      $sum: {
        $cond: ["$read", 0, 1]
      },
    },
    createdAt: {
      $first: "$createdAt",
    },
  },
},

$lookup: {
  from: "users",
  localField: "_id",
  foreignField: "_id",
  as: "user",
},
}, {
$sort: {
  createdAt: -1,
},
}, {
$project: {
  _id: 1,
  count: 1,
  createdAt: 1,
  user: 1,
},
}, ]);

我想要获取的数据示例 比如说，我们有两个用户互相写信。 用户1被称为帕皮·约翰逊，另一个是米歇尔王子

米歇尔王子向帕皮·约翰逊发送两条消息。 由于帕皮·约翰逊尚未阅读米歇尔亲王的信息，因此当帕皮·约翰逊请求他发送或接收的信息时，结果应该是：

{
_id: 5f8cf7e3c68dd730b5edb8a9, // the ID of Prince Michel
count: 2, // number of message unread send by Prince Michel to Papi johnson
createdAt: 2020-10-19T02:27:39.759Z, // the last message receive
user: [ [Object] ] // in then the user info of Prince Michel 
}

{
_id: 5f8cf8f5b76f3e3d5e6e249f,// the ID of Papi johnson
count: 0, // number of message unread send by Papi johnson to Prince Michel  
createdAt: 2020-10-19T02:27:39.759Z,
user: [ [Object] ]// in then the user info of Papi johnson
}

当米歇尔王子请求接收他发送或接收的信息时，结果应该是：

{
_id: 5f8cf7e3c68dd730b5edb8a9, // the ID of Prince Michel
count: 2, // number of message unread send by Prince Michel to Papi johnson
createdAt: 2020-10-19T02:27:39.759Z, // the last message receive
user: [ [Object] ] // in then the user info of Prince Michel 
}

{
_id: 5f8cf8f5b76f3e3d5e6e249f,// the ID of Papi johnson
count: 0, // number of message unread send by Papi johnson to Prince Michel  
createdAt: 2020-10-19T02:27:39.759Z,
user: [ [Object] ]// in then the user info of Papi johnson
}

这就是我得到的结果： 照片中的示例

**问题是我收到的两个用户的未读邮件数量相同。 我认为问题可能是“$group”和“$sum”查询不仅计算用户收到的未读消息，还计算用户发送或接收的所有未读消息。 我已经写了10多天的博客了，我不知道该怎么做。 **

当Papi johnson请求他发送或接收的消息时，结果是：

{
_id: 5f8cf7e3c68dd730b5edb8a9, // the ID of Prince Michel
count: 2, 
// I think here the "$ group" and "$ sum" 
//query does not count only unread message received by the user,
// but rather all unread message that is sent or received by the user.
createdAt: 2020-10-19T02:27:39.759Z, // the last message receive
user: [ [Object] ] // in then the user info of Prince Michel 
}

{
_id: 5f8cf8f5b76f3e3d5e6e249f,// the ID of Papi johnson
count: 2, 
// I think here the "$ group" and "$ sum" 
//query does not count only unread message received by the user,
// but rather all unread message that is sent or received by the user.
createdAt: 2020-10-19T02:27:39.759Z,
user: [ [Object] ]// in then the user info of Papi johnson
}

当米歇尔王子请求接收他发送或接收的信息时，结果是：

{
_id: 5f8cf7e3c68dd730b5edb8a9, // the ID of Prince Michel
count: 2, 
// I think here the "$ group" and "$ sum" 
//query does not count only unread message received by the user,
// but rather all unread message that is sent or received by the user.
createdAt: 2020-10-19T02:27:39.759Z, // the last message receive
user: [ [Object] ] // in then the user info of Prince Michel 
}

{
_id: 5f8cf8f5b76f3e3d5e6e249f,// the ID of Papi johnson
count: 2, 
// I think here the "$ group" and "$ sum" 
//query does not count only unread message received by the user,
// but rather all unread message that is sent or received by the user.
createdAt: 2020-10-19T02:27:39.759Z,
user: [ [Object] ]// in then the user info of Papi johnson
}

---

你能发布你现在得到的结果和你的期望吗？你好@wak786我做了一些更新，我希望能回答你的问题。谢谢你，我现在回答这个问题了。你能提供一些示例文档吗？这样我就可以用它们来进行查询了。您可以创建

Mongo游乐场

，并与我共享链接@这里是wak786的链接，你能发布你现在得到的结果和你的期望吗？你好@wak786我做了一些更新，我希望能回答你的问题。谢谢你，我现在回答这个问题了。你能提供一些示例文档吗？这样我就可以用它们来进行查询了。您可以创建

Mongo游乐场

，并与我共享链接@wak786这里是链接