映射数组导致 mongodb 聚合

发布于04月09日

我有以下MongoDB查询:

const vaccination = await Schedule.aggregate([
        { $match: { status: ScheduleStatus.Published } },
        { "$unwind": { "path": "$vaccines", "preserveNullAndEmptyArrays": true } },

        {
            "$group": {
                "_id": "$vaccines.vaccine",
                "count": { "$sum": "$vaccines.stok" },

            }
        },
        {
            $lookup: { from: 'vaccines', localField: '_id', foreignField: '_id', as: 'vaccine' },
        },
        {
            $project: {

                "count": 1,
                "vaccine": { "$arrayElemAt": ["$vaccine.name", 0] }


            }
        }

    ]);

并返回以下结果:

[
    {
        "_id": "61efd8a812432135c08a748d",
        "count": 20,
        "vaccine": "Sinovac"
    }
]

有没有办法让输出成为一个值数组，比如:

[["Sinovac",20]]

谢谢，对不起，我英语不好

推荐答案

因此，您无法获得所需的确切 struct ，根据定义，聚合框架返回一个"文档"数组，文档的形式为{key: value}，但您可以返回以下 struct :

[
  {
    "values": [
      "61efd8a812432135c08a748d",
      20,
      "Sinovac"
    ]
  }
]

通过这条管道:

db.collection.aggregate([
  {
    $project: {
      _id: 0,
      values: {
        $map: {
          input: {
            "$objectToArray": "$$ROOT"
          },
          as: "item",
          in: "$$item.v"
        }
      }
    }
  }
])

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