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node.js - 猫鼬聚合不返回最新文档

问题描述

我有一个返回文档的聚合，但我需要它返回一个文档，该文档是集合 messageTrackingId 中的最新文档。在该字段中具有最新值的那个creationDate我有一种方法可以完成此操作，但我不断收到不是最新的返回文档，我不知道为什么。目的是向用户显示该用户与另一个用户之间发送的最后一条消息的时间戳，无论是谁发送的。感谢任何帮助。

app.get("/api/messages", (req, res, next) => {
  query = {};
  inbox = false;
  messageId = false;
  console.log(req.query.recipientId);
  if (req.query.recipientId) {
    query = { recipientId: req.query.recipientId };
    inbox = true;

    Messages.aggregate([
      {
        $match: {
          $or: [
            { recipientId: req.query.recipientId },
            { creator: mongoose.Types.ObjectId(req.query.recipientId) }
          ]
        }
      },
      {
        $addFields: {
          conversant: {
            $cond: [
              { $ne: ["$recipientId", req.query.recipientId] },
              "$recipientId",
              "$creator"
            ]
          }
        }
      },
      {
        $sort: { creationDate: 1 }
      },
      {
        $group: {
          _id: "$conversant",
          message: { $last: "$message" },
          recipientId: { $last: "$recipientId" },
          creator: { $last: "$creator" },
          messageTrackingId: { $last: "$messageTrackingId" },
          recipient: { $last: "$recipient" },
          creationDate: { $last: "$creationDate" }
        }
      },
      {
        $lookup: {
          from: "users",
          let: { creator: "$creator" },
          pipeline: [
            { $match: { $expr: { $eq: ["$_id", "$$creator"] } } },
            { $project: { instagramName: 1 } }
          ],
          as: "creatorName"
        }
      }
    ]).then(documents => {


      if (inbox === true) {
        res.status(200).json({
          message: "User's Inbox Retrieved!",
          posts: documents
        });
      }

    });

我清理了消息表并来回发送了3条消息进行演示。当我重新加载页面时，我只收到 JSON 响应中的 2 个文档，而不是最新的一个。在收到的 2 个中，它们似乎都不是最新的。我不确定为什么它不返回一个。请参阅下面的页面加载输出。

留言：

/* 1 */
{
    "_id" : "5e16463be5fcba1d2c56ebb7",
    "creator" : "5e0a1d41f86e1e4234fc1a77",
    "recipient" : "andy",
    "recipientId" : "5df0014e25ee451beccf588a",
    "message" : "First message",
    "messageTrackingId" : "17c4fc99-d92f-46ef-9bae-1408f415287a",
    "creatorName" : "buyer1",
    "creationDate" : ISODate("2020-01-08T21:14:35.104Z"),
    "__v" : 0.0
}

/* 2 */
{
    "_id" : "5e16464de5fcba1d2c56ebb9",
    "creator" : "5df0014e25ee451beccf588a",
    "recipient" : "buyer1",
    "recipientId" : "5e0a1d41f86e1e4234fc1a77",
    "message" : "Second Message",
    "messageTrackingId" : "17c4fc99-d92f-46ef-9bae-1408f415287a",
    "creatorName" : "andy",
    "creationDate" : ISODate("2020-01-08T21:14:53.618Z"),
    "__v" : 0.0
}

/* 3 */
{
    "_id" : "5e16465ce5fcba1d2c56ebbb",
    "creator" : "5e0a1d41f86e1e4234fc1a77",
    "recipient" : "andy",
    "recipientId" : "5df0014e25ee451beccf588a",
    "message" : "Third Message",
    "messageTrackingId" : "17c4fc99-d92f-46ef-9bae-1408f415287a",
    "creatorName" : "buyer1",
    "creationDate" : ISODate("2020-01-08T21:15:08.500Z"),
    "__v" : 0.0
}

用户：

/* 1 */
{
    "_id" : "5df00d08c713f722909c99c1",
    "email" : "joe@gmail.com",
    "password" : "$2b$10$5eWhwL4RNT8TyQRCC191J.myYBwFcJ8hCARqGfofYWUmRaq6jJFQm",
    "instagramName" : "joe",
    "over21" : "Yes",
    "role" : "Artist",
    "fullName" : "testdsfdfsfs",
    "address1" : "adfsdf",
    "address2" : "dssdf",
    "city" : "sdfsdfsdf",
    "state" : "dsffsdsd",
    "zip" : "dsdfsdf",
    "passwordCreated" : ISODate("2020-01-07T23:46:57.861Z"),
    "__v" : 0
}

/* 2 */
{
    "_id" : "5df0014e25ee451beccf588a",
    "email" : "andy@gmail.com",
    "password" : "$2b$10$fNHmIoDb4mX6x.YeMLXHbu2yIaeW6HVQvNpZR8Nt/a4xVFkhxM1Ey",
    "instagramName" : "andy",
    "over21" : "Yes",
    "role" : "Artist",
    "fullName" : "dsfdsfdfdsf",
    "address1" : "111",
    "address2" : "111",
    "city" : "atlanta",
    "state" : "ga",
    "zip" : "33222",
    "passwordCreated" : ISODate("2019-12-19T15:29:46.528Z"),
    "__v" : 0
}

所需输出（返回每个用户的最后一条消息）：

/* 1 */
{
    "_id" : {
        "conversant" : "5df0014e25ee451beccf588a",
        "recipient" : "andy"
    },
    "message" : "Third Message",
    "recipientId" : "5df0014e25ee451beccf588a",
    "creator" : "5e0a1d41f86e1e4234fc1a77",
    "messageTrackingId" : "17c4fc99-d92f-46ef-9bae-1408f415287a",
    "recipient" : "andy",
    "creationDate" : ISODate("2020-01-08T21:15:08.500Z"),
    "creatorName" : [ 
        {
            "_id" : "5df0014e25ee451beccf588a",
            "instagramName" : "andy"
        }
    ]
}

/* 2 */
{
    "_id" : {
        "conversant" : "5df0014e25ee451beccf588a",
        "recipient" : "buyer1"
    },
    "message" : "Second Message",
    "recipientId" : "5e0a1d41f86e1e4234fc1a77",
    "creator" : "5df0014e25ee451beccf588a",
    "messageTrackingId" : "17c4fc99-d92f-46ef-9bae-1408f415287a",
    "recipient" : "buyer1",
    "creationDate" : ISODate("2020-01-08T21:14:53.618Z"),
    "creatorName" : [ 
        {
            "_id" : "5df0014e25ee451beccf588a",
            "instagramName" : "andy"
        }
    ]
}

标签： node.jsmongodbmongooseaggregation-framework

解决方案

改变必须是

1）如果我在这个阶段理解正确，你想recipientId对一个字段进行分组（因为你不能对单个值的两个字段进行分组）所以你正在创建一个名为的新字段conversant，所以它必须是$eq或者你需要交换recipientId& creator & 也必须是$toString：

{
      $addFields: {
        conversant: {
          $cond: [
            { $eq: ["$recipientId", req.query.recipientId] },
            "$recipientId",
            {$toString : "$creator"} 
          ]
        }
      }
    }

2）您不需要这个$sort阶段，因为所有最新添加的集合都将在最后添加（期望creationDate一旦创建但从未更新）：

// Not useful
{
     $sort: { creationDate: 1 }
}

此外，您还需要_id: { conversant: "$conversant", recipient: '$recipient' }根据基于user. 在$lookup改变这个let: { conversant: "$_id.conversant" }。

尝试这个 ：

 Messages.aggregate([
    {
        $match: {
            $or: [
                { recipientId: req.query.recipientId },
                { creator: mongoose.Types.ObjectId(req.query.recipientId) }
            ]
        }
    },
    {
        $addFields: {
            conversant: {
                $cond: [
                    { $eq: ["$recipientId", req.query.recipientId] },
                    "$recipientId",
                    { $toString: "$creator" }
                ]
            }
        }
    },
    {
        $group: {
            _id: { conversant: "$conversant", recipient: '$recipient' },
            message: { $last: "$message" },
            recipientId: { $last: "$recipientId" },
            creator: { $last: "$creator" },
            messageTrackingId: { $last: "$messageTrackingId" },
            recipient: { $last: "$recipient" },
            creationDate: { $last: "$creationDate" }
        }
    },
    {
        $lookup: {
            from: "users",
            let: { conversant: "$_id.conversant" },
            pipeline: [
                { $match: { $expr: { $eq: ["$_id", "$$conversant"] } } },
                { $project: { instagramName: 1 } }
            ],
            as: "creatorName"
        }
    },
     // this is optional only if you wanted to return latest document irrespective of user.
     { $sort: { creationDate: -1 } }
])

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