总结mongodb中多个子文档的值 [英] sum up value from multiple subdocuments in mongodb

问题描述

我具有以下数据结构：

{
  "_id" : ObjectId("4e96f771e016b98aa63d88c9"),
  "goals" : {
    "4809" : {
      "VisitsBeforeGoal" : 12,
      "pagesBeforeGoal" : 16
    },
    "4810" : {
      "VisitsBeforeGoal" : 2,
      "pagesBeforeGoal" : 6
    },
    "4811" : {
      "VisitsBeforeGoal" : 3,
      "pagesBeforeGoal" : 8
    }
  },
  "totalPages" : 246,
  "totalVisits" : 114
}

4809、4810和4811是未知的目标ID，例如

4809, 4810 and 4811 is goalID's that are not know, e.g. dynamic.

现在，我要获取的是每个目标的 VisitsBeforeGoal和 pagesBeforeGoal的总和。

Now what i want is to get the sum of "VisitsBeforeGoal" on each goal and "pagesBeforeGoal" and a sum of goals. Something like:

{
  goals:[
    {
          "goalID" : 4809,
          "VisitsBeforeGoal" : 245,
          "pagesBeforeGoal" : 632,
          "sum" : 45,    
    }
  ]
}

我似乎不知道如何进入每个子文档，因为我不知道goalID。我尝试过类似 goals。$。VisitsBeforeGoal的操作，但这似乎不起作用。

I cant seem to figure out how to get into each subdocument, as i dont know the goalID. I tried somehting like "goals.$.VisitsBeforeGoal" but that did not seem to work.

推荐答案

您的数据结构存在问题。为了使 goals。$。VisitsBeforeGoal 起作用，您需要一个数组。因此，您的结构必须为

Your data structure is problematical. In order to make goals.$.VisitsBeforeGoal work, you need an array. So your structure must be

"goals" : [ {
        "id" : 4809,
        "VisitsBeforeGoal" : 12,
        "pagesBeforeGoal" : 16
    },
    {
        "id" : 4810,
        "VisitsBeforeGoal" : 2,
        "pagesBeforeGoal" : 6
    },
    {
        "id" : 4811,
        "VisitsBeforeGoal" : 3,
        "pagesBeforeGoal" : 8
    }
]

使用动态键不是一个好的选择。如果您有机会更改自己的结构，我建议您更改它。

Working with dynamic keys is not a good choice. If you have chance to change your structure, I would advice you to change it.

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