MongoDB中文档引用关系的Mongoose实现答案

【问题标题】：Mongoose implementation for Document Referenced Relationship in MongoDBMongoDB中文档引用关系的Mongoose实现
【发布时间】：2019-10-30 21:18:18
【问题描述】：

我需要使用文档引用关系（而不是嵌入文档）进行聚合查询。我可以使用 mongo shell 进行该查询，但在使用 mongoose 的等效实现方面遇到了困难。

我已经尝试过虚拟填充方法，但这也返回了空数组。这是一些定义上下文的代码以及我的 mongo 查询。我在父文档和子文档之间建立了一对多的关系。

    //Parent Document
    db.artists.insert(
        {
            _id : 4,
            artistname : "Rush"
        }
    )

    //Child Documents
    db.musicians.insert(
        {
            _id : 9,
            name : "Geddy Lee",
            instrument : [ "Bass", "Vocals", "Keyboards" ],
            artist_id : 4
        }
    )
    db.musicians.insert(
        {
            _id : 10,
            name : "Alex Lifeson",
            instrument : [ "Guitar", "Backing Vocals" ],
            artist_id : 4
        }
    )
    db.musicians.insert(
        {
            _id : 11,
            name : "Neil Peart",
            instrument : "Drums",
            artist_id : 4
        }
    )

    //Query
    db.artists.aggregate([
        {
          $lookup:
            {
              from: "musicians",
              localField: "_id",
              foreignField: "artist_id",
              as: "band_members"
            }
       },
       { $match : { artistname : "Rush" } }
    ]).pretty()

    //Result
    {
        "_id" : 4,
        "artistname" : "Rush",
        "band_members" : [
            {
                "_id" : 9,
                "name" : "Geddy Lee",
                "instrument" : [
                    "Bass",
                    "Vocals",
                    "Keyboards"
                ],
                "artist_id" : 4
            },
            {
                "_id" : 10,
                "name" : "Alex Lifeson",
                "instrument" : [
                    "Guitar",
                    "Backing Vocals"
                ],
                "artist_id" : 4
            },
            {
                "_id" : 11,
                "name" : "Neil Peart",
                "instrument" : "Drums",
                "artist_id" : 4
            }
        ]
    }

//I've tried using populate, as well as aggregate. Here are both the implementations:

//Using populate
ArtistSchema.virtual('members', {
   ref: 'MusicianCollection',
   localField: '_id',
   foreignField: 'artist_id',
   justOne: false,
   options: {limit: 5}
})

this.ArtistModel.findById(id).populate('members').exec((err, data) => {
      if (err) console.log(err)
      else artist = data
    })

//in this i get a features array, but its empty


//Using aggregate
let artist = await this.ArtistModel.aggregate([
     { $match: { _id: id} },
     { $lookup: {
       from: 'Musicians',
       localField: '_id',
       foreignField: 'artist_id',
       as: 'members'
     } }
   ]);

//in this the request times out

【问题讨论】：

请说明你用mongoose做了什么？
@RaviShankarBharti 我已经更新了代码 sn-p。请看一看。
Amazon DocumentDB 现在支持 $lookup：aws.amazon.com/about-aws/whats-new/2019/10/…

标签： mongodb mongoose mongoose-populate aws-documentdb-mongoapi aws-documentdb

【解决方案1】：

实施非常明确。由于一些依赖注入问题，我的无法正常工作。虽然这是参考的解决方案：

为避免在跨集合引用文档时使用引用 ID 数组，虚拟填充是可行的方法。

ArtistSchema.virtual('members', {
   ref: 'MusicianCollection',
   localField: '_id',
   foreignField: 'artist_id',
   justOne: false,
   options: {limit: 5}
})

band = await this.ArtistModel.findById(id).populate('members').exec()

【讨论】：