mongodb - 蒙戈 : How to group by $week but return start date and end date of each week instead?

Question

我正在使用 $group by $week。它返回一年中的#week，但我想要开始日期，每周的结束日期而不是

示例:

当前结果:

[{
    "_id" : 20,
    "averageValue" : null
},
{
    "_id" : 21,
    "averageValue" : 28.1875
}]

期待:

[{
    "_id" : [{ start: "2021-01-01", "end": "2021-01-07" }],
    "averageValue" : null
},
{
    "_id" : [{ start: "2021-01-08", "end": "2021-01-14" }],
    "averageValue" : 28.1875
}]

Answer 1

虽然它是可行的，但会降低代码的可读性和复杂性。

我将重写 $group 阶段以包括 year 和 weeks 并添加 $project 阶段根据要求格式化数据。

db.collection.aggregate([
  {
    "$group": {
      "_id": {
        "week": {
          "$week": {"$subtract": ["$at", 25200000]}  // <-- Changes timezone to -07:00
        },
        "year": {
          "$year": {"$subtract": ["$at", 25200000]}  // <-- Changes timezone to -07:00
        },
      },
      // <-- Add keys to be added in group along with its logics
      "averageValue": {
        "$avg": "$readings.level_1"
      }
    },
  },
  {
    "$project": {
      "_id": {
        "startDate": {
          "$dateToString": {
            "date": {
              "$dateFromParts": {
                "isoWeekYear": "$_id.year",
                "isoWeek": "$_id.week"
              }
            },
            "format": "%Y-%m-%d",
          },
        },
        "endDate": {
          "$dateToString": {
            "date": {
              "$add": [
                {
                  "$dateFromParts": {
                    "isoWeekYear": "$_id.year",
                    "isoWeek": "$_id.week"
                  }
                },
                518400000,
              ],
            },
            "format": "%Y-%m-%d",
          },
        },
      },
      // <-- Add remaining keys to be projected
      "averageValue": 1,
    },
  },
])

如果您需要解释每个阶段和使用的运算符以及我为什么使用它，请告诉我。

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