貓鼬按升序排序

const followingUsers = await User.find({ _id: { $in: foundUser.followings } })
const getFeedData = async() => {
    let data = []
    for (let user of followingUsers) {
        const userPosts = user.posts
        for (let post of userPosts) {
            const posts = await Post.find({ _id: post })
            for (let post of posts) {
                const foundPost = await Post.findById(post._id).sort({ createdAt: -1 })
                data.push(foundPost)
            }
        }
    }
    return data
}
const posts = await getFeedData()

這是一些示例資料，假設有兩個相同的用戶，我想獲取他們的帖子并按升序對它們進行排序，這兩個用戶是我關注的用戶，我需要獲取他們的所有帖子并在新聞提要中顯示它們

   "user": [
    {
      _id: ObjectId("625c053cfdd023e3713b297f"),
      email: "[email protected]",
      isAdmin: false,
      chats: [],
      blockedChats: [],
      feedback: [],
      plans: [],
      posts: [
        ObjectId("625c0577fdd023e3713b29c7"),
        ObjectId("625c0582fdd023e3713b29f5"),
        ObjectId("625c075f8f794ea1fcf6c6af"),
        ObjectId("625c4a742db74795a43d5243")
      ],
      opportunities: [],
      username: "sam",
      createdAt: ISODate("2022-04-17T12:17:01.095Z"),
      updatedAt: ISODate("2022-04-17T17:12:20.341Z"),
      __v: 4
    }
  ],
  "post": [
    {
      _id: ObjectId("625c0577fdd023e3713b29c7"),
      postText: "hi this is sam\r\n",
      likes: [],
      likesCount: [],
      timePosted: ISODate("2022-04-17T12:09:05.535Z"),
      postImage: [],
      user: ObjectId("625c053cfdd023e3713b297f"),
      createdAt: ISODate("2022-04-01T00:00:00.00Z")
    },
    {
      _id: ObjectId("625c075f8f794ea1fcf6c6af"),
      postText: "it works !!!",
      likes: [],
      likesCount: [],
      timePosted: ISODate("2022-04-17T12:20:08.794Z"),
      postImage: [],
      user: ObjectId("625c053cfdd023e3713b297f"),
      createdAt: ISODate("2022-04-17T12:26:07.075Z"),
      updatedAt: ISODate("2022-04-17T12:26:07.075Z")
    }
  ]

蒙古游樂場

一切正常，除了我檢索回來的檔案不是按升序排列的，這也可能是由于回圈，或者可能對資料庫執行盡可能少的查詢，這里有什么問題可以幫忙嗎？

uj5u.com熱心網友回復：

您可能可以通過$lookup.

const getFeedData = async() => {
    const foundPost = await User.aggregate([
        {
          $match: {
            _id: {
              $in: foundUser.followings
            }
          }
        },
        {
          "$lookup": {
            "from": "post",
            "let": {
              posts: "$posts"
            },
            "pipeline": [
              {
                $match: {
                  $expr: {
                    "$in": [
                      "$_id",
                      "$$posts"
                    ]
                  }
                }
              },
              {
                "$sort": {
                  createdAt: -1
                }
              }
            ],
            "as": "postLookup"
          }
        },
        {
          "$unwind": "$postLookup"
        },
        {
          "$replaceRoot": {
            "newRoot": "$postLookup"
          }
        }
      ])
    return foundPost
}
const posts = await getFeedData()

這是Mongo游樂場供您參考。

標籤：节点.js mongodb 表示 猫鼬 mongodb查询

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