arrays - 聚合嵌套的对象数组

Question

我有以下文档结构：

{
  "_id": "5d2708ff79263ba40e54c08c",
  "meta": {
    "uid": "dd41ca10-a3c2-11e9-a1dd-fbec9d04cb25",
    "firmware": "0.0.1",
    "timestamp": "2019-07-11T10:01:35.264Z"
  },
  "sensors": [
    {
      "_id": "5d2708ff79263ba40e54c08e",
      "name": "sensor1",
      "value": 0.09050827850822706
    },
    {
      "_id": "5d2708ff79263ba40e54c08d",
      "name": "sensor2",
      "value": 0.06592630654288716
    }
  ]
}

我要做的是每分钟选择所有文档，然后计算每个传感器的平均值并得到如下结果：

{
  "_id": "5d2708ff79263ba40e54c08c",
  "meta": {
    "uid": "dd41ca10-a3c2-11e9-a1dd-fbec9d04cb25",
    "firmware": "0.0.1",
    "timestamp": "2019-07-11T10:01:35.264Z"
  },
  "sensors": [
    {
      "_id": "5d2708ff79263ba40e54c08e",
      "name": "sensor1",
      "avg": 0.1111111
    },
    {
      "_id": "5d2708ff79263ba40e54c08d",
      "name": "sensor2",
      "avg": 0.2222222
    }
  ]
}

经过多年使用关系数据库后，这有点令人困惑。