MongoDB 嵌套对象聚合计数

Question

我有一个高度嵌套的 mongoDB 对象集，我想计算符合给定条件的子文档的数量 编辑：（在每个文档中） .例如：

{"_id":{"chr":"20","pos":"14371","ref":"A","alt":"G"},
"studies":[
    {
        "study_id":"Study1",
        "samples":[
            {
                "sample_id":"NA00001",
                "formatdata":[
                    {"GT":"1|0","GQ":48,"DP":8,"HQ":[51,51]}
                ]
            },
            {
                "sample_id":"NA00002",
                "formatdata":[
                    {"GT":"0|0","GQ":48,"DP":8,"HQ":[51,51]}
                ]
            }
        ]
    }
]
}
{"_id":{"chr":"20","pos":"14372","ref":"T","alt":"AA"},
"studies":[
    {
        "study_id":"Study3",
        "samples":[
            {
                "sample_id":"SAMPLE1",
                "formatdata":[
                    {"GT":"1|0","GQ":48,"DP":8,"HQ":[51,51]}
                ]
            },
            {
                "sample_id":"SAMPLE2",
                "formatdata":[
                    {"GT":"1|0","GQ":48,"DP":8,"HQ":[51,51]}
                ]
            }
        ]
    }
]
}
{"_id":{"chr":"20","pos":"14373","ref":"C","alt":"A"},
"studies":[
    {
        "study_id":"Study3",
        "samples":[
            {
                "sample_id":"SAMPLE3",
                "formatdata":[
                    {"GT":"0|0","GQ":48,"DP":8,"HQ":[51,51]}
                ]
            },
            {
                "sample_id":"SAMPLE7",
                "formatdata":[
                    {"GT":"0|0","GQ":48,"DP":8,"HQ":[51,51]}
                ]
            }
        ]
    }
]
}

我想知道有多少个子文档包含 GT:"1|0"，在本例中，第一个文档中为 1，第二个文档中为两个，第三个文档中为 0。我试过 unwind 和 aggregate 函数，但我显然没有做正确的事情。当我尝试通过 "GT" 字段计算子文档时，mongo 抱怨：

db.collection.aggregate([{$group: {"$studies.samples.formatdata.GT":1,_id:0}}])

由于我的群组名称不能包含“.”，但如果我将它们排除在外：

db.collection.aggregate([{$group: {"$GT":1,_id:0}}])

它抱怨是因为“$GT 不能是运算符名称”

有什么想法吗？

Answer 1

使用数组时需要处理$unwind，需要处理3次：

 db.collection.aggregate([

     // Un-wind the array's to access filtering 
     { "$unwind": "$studies" },
     { "$unwind": "$studies.samples" },
     { "$unwind": "$studies.samples.formdata" },

     // Group results to obtain the matched count per key
     { "$group": {
         "_id": "$studies.samples.formdata.GT",
         "count": { "$sum": 1 }
     }}
 ])

理想情况下，您希望过滤您的输入。可能使用 $match both before and after $unwind is processed and using a $regex 来匹配数据以“1”开头的文档。

 db.collection.aggregate([

     // Match first to exclude documents where this is not present in any array member
     { "$match": { "studies.samples.formdata.GT": /^1/ } },

     // Un-wind the array's to access filtering 
     { "$unwind": "$studies" },
     { "$unwind": "$studies.samples" },
     { "$unwind": "$studies.samples.formdata" },

     // Match to filter
     { "$match": { "studies.samples.formdata.GT": /^1/ } },

     // Group results to obtain the matched count per key
     { "$group": {
         "_id": {
              "_id": "$_id",
              "key": "$studies.samples.formdata.GT"
         },
         "count": { "$sum": 1 }
     }}
 ])

请注意，在所有情况下，"dollar $" 前缀条目都是指代文档属性的 "variables"。这些是 "values" 使用右侧的输入。左侧 "keys" 必须指定为纯字符串键。不能使用变量来命名键。

Answer 2

https://mongoplayground.net/p/DpX6cFhR_mm

db.collection.aggregate([
  {
    "$unwind": "$tags"
  },
  {
    "$match": {
      "$or": [
        {
          "tags.name": "Canada"
        },
        {
          "tags.name": "ABC"
        }
      ]
    }
  },
  {
    "$group": {
      "_id": null,
      "count": {
        "$sum": 1
      }
    }
  }
])

MongoDB 嵌套对象聚合计数

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mongodb

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aggregation-framework