猫鼬按升序排序

Question

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()

这是一些示例数据，假设有两个相同的用户我想获取他们的帖子并按升序对它们进行排序，那些两个用户是我关注的用户，我需要获取他们所有的帖子并在动态消息中显示它们

   "user": [
    {
      _id: ObjectId("625c053cfdd023e3713b297f"),
      email: "user1@yahoo.com",
      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")
    }
  ]

Mongo playground

一切正常，除了我正在检索的文档不是按升序排列，也可能是由于循环，或者对数据库执行尽可能少的查询，这是什么问题有人可以帮忙吗？

Answer 1

您可能可以通过 $lookup 实现相同的逻辑。

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()

这里是Mongo playground供您参考。

猫鼬按升序排序

mongoose sorting by ascending order

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