Mongodb 的 $match 返回同一文档的多次出现

Question

我的文档结构如下：

{
name: "some user name",
  cvs: [{
    title: 'Cv title'
    technologies: [
      {
        text: 'JavaScript',
        main: true
      },
      {
        text: "AngularJs",
        main: true
      }
    ]
  }]
}

当我进行以下聚合时（db 中只有一个文档）：

db.users.aggregate([

{"$unwind": "$cvs"},
{"$unwind": "$cvs.technologies"},
{"$match": {
    "cvs.isBlocked": false,
    "cvs.moderated": true,
    "cvs.isVisible": true,
    "cvs.technologies.main": true 
    }
 },
  {"$project": {
      "type": "$cvs.occupationType",
      "proficiency": "$cvs.proficiencyLevel",
      "_id": "$cvs._id",
      "title": "$cvs.title",
      "technologies": "$cvs.technologies.text",
     }}
])

我得到一个包含两个元素的数组（但这是同一个文档），只是因为有两种技术匹配

"cvs.technologies.main": true

[
    {
        "_id" : ObjectId("5629e813279b62fe075fbd4c"),
        "type" : "Frontend",
        "proficiency" : "Middle",
        "title" : "Frontend developer",
        "technologies" : "JavaScript",
    },
    {
        "_id" : ObjectId("5629e813279b62fe075fbd4c"),
        "type" : "Frontend",
        "proficiency" : "Middle",
        "title" : "Frontend developer",
        "technologies" : "Ruby",
    }
]

我怎样才能得到这个结果？：

[
    {
        "_id" : ObjectId("5629e813279b62fe075fbd4c"),
        "type" : "Frontend",
        "proficiency" : "Middle",
        "title" : "Frontend developer",
        "technologies" : ["JavaScript", "Ruby"],
    }
]

Answer 1

运行以下管道，其中添加了额外的 $match 和 $group 管道步骤，以便 optimize 聚合管道（在 $unwind 之前放置一个 $match 管道以过滤掉通过管道的不需要的文档）获得所需的结果（使用 $group strong> 运算符按给定字段对文档进行分组，使用 $push 累加器创建数组）：

db.users.aggregate([
    {
        "$match": {
            "cvs.isBlocked": false,
            "cvs.moderated": true,
            "cvs.isVisible": true,
            "cvs.technologies.main": true 
        }
    },
    {"$unwind": "$cvs"},
    {"$unwind": "$cvs.technologies"},
    {
        "$match": {
            "cvs.isBlocked": false,
            "cvs.moderated": true,
            "cvs.isVisible": true,
            "cvs.technologies.main": true 
        }
    },
    {
        "$group": {
            "_id": {
                "type": "$cvs.occupationType",
                "proficiency": "$cvs.proficiencyLevel",
                "_id": "$cvs._id",
                "title": "$cvs.title"               
            },
            "technologies": {
                "$push": "$cvs.technologies.text"
            }
        }
    },
    {
        "$project": {
            "type": "$_id.type",
            "proficiency": "$_id.proficiency",
            "_id": "$_id._id",
            "title": "$_id.title",
            "technologies": 1,
        }
    }
])