mongodb 中的聊天集合查询

Question

{
  "_id": "654f4d7cbb027c35a0b90529",
  "msg": "test message",
  "createdat": "2023-11-11T09:46:41.872Z",
  "dateseen": "2023-11-11T09:55:56.596Z",
  "fromid": "eb78a1f79938f5eb193b63fc13b3250",
  "toid": "7b987d98718041abb3b9a85b5c96214a",
  "deleted1": false,
  "deleted1at": null,
  "deleted2": false,
  "deleted2at": null,
  "type": 1
}

我有一个像上面这样的聊天集合。从这个集合中，我需要一个查询，将某个用户 ID 发送到聊天 DM，并检索最后一条消息的人员、最后一条消息和未读消息的数量。我尝试了很多，但我无法弄清楚。有人可以帮忙吗？

我需要与此类似的输出；

{
    "body": [
        {
            "id": "c5e8b02a94984fe38e7ff35131890b55",
            "unSeenMsgCount": 0,
            "lastMessage": {
                "fromId": "eb78a1f74f274353b63fc13b3250",
                "toId": "c5e8b02a94984fe7ff35131890b55",
                "message": "string",
                "dateSent": 1704889808607,
                "type": 1
            }
        }
    ],
    "header": null
}

这是最接近解决方案的代码，但仍然没有完全满足我的需求。不仅看不见的消息会错误地传入，而且还会从 to id 和 id 返回两个不同的聊天记录。

db.collection.aggregate([
  {
    $match: {
      $or: [
        { "fromid": userID, "deleted1": false },
        { "toid": userID, "deleted2": false }
      ]
    }
  },
  {
    $group: {
      _id: {
        $cond: {
          if: {
            $or: [
              { $and: [{ $eq: ["$fromid", userID] }, { $ne: ["$toid", userID] }] },
              { $and: [{ $eq: ["$toid", userID] }, { $ne: ["$fromid", userID] }] }
            ]
          },
          then: "$toid",
          else: "$fromid"
        }
      },
      lastMessage: {
        $last: {
          $cond: {
            if: {
              $or: [
                { $and: [{ $eq: ["$toid", userID] }, { $ne: ["$fromid", userID] }] },
                { $and: [{ $eq: ["$fromid", userID] }, { $ne: ["$toid", userID] }] }
              ]
            },
            then: "$$ROOT",
            else: null
          }
        }
      },
      unseenCount: {
        $sum: {
          $cond: {
            if: {
              $and: [
                { $eq: ["$toid", userID] },
                { $eq: ["$dateseen", null] }
              ]
            },
            then: 1,
            else: 0
          }
        }
      }
    }
  },
  {
    $sort: { "lastMessage.createdat": -1 }
  },
  {
    $replaceRoot: {
      newRoot: {
        $mergeObjects: ["$lastMessage", { "unSeenMsgCount": "$unseenCount" }]
      }
    }
  },
  {
    $skip: offset
  },
  {
    $limit: limit
  }
])

Answer 1

假设你有一个想要查询的 userId 变量，并考虑到你的集合结构，也许你会喜欢这个

db.chats.aggregate([
{
    $match: {
        $or: [
            { fromid: userId },
            { toid: userId }
        ],
        deleted1: false, // Assuming this flag is for message deletion status
        deleted2: false
    }
},
{
    $sort: { createdat: -1 }
},
{
    $group: {
        _id: {
            $cond: {
                if: { $eq: ["$fromid", userId] },
                then: "$toid",
                else: "$fromid"
            }
        },
        lastMessage: { $first: "$msg" },
        unreadCount: {
            $sum: {
                $cond: [
                    { $and: [{ $ne: ["$fromid", userId] }, { $eq: ["$dateseen", null] }] },
                    1,
                    0
                ]
            }
        }
    }
}]);