MongoDB：$lookup 数组后的 $sum

Question

我有这个查询，并且正在使用$lookup，之后我想对value查找提供的数组中的求和。

我的查询（我正在使用猫鼬）：

  User.aggregate([{
      $match: {
        storeKey: req.body.store,
      }
    },
    {
      $group: {
        _id: {
          id: "$_id",
          name: "$name",
          cpf: "$cpf",      
          phone: "$phone",
          email: "$email",
          birthday: "$birthday"      
        },
        totalServices: {
          $sum: "$services"
        }
      }
    },
    {
      $lookup: {
        from: "schedules",
        localField: "_id.phone",
        foreignField: "customer.phone",
        as: "user_detail"
      }  
    },
    { $project: { "user_detail.value": 1 } },
  ])

我的查询结果（样本集合）：

{
        "_id": {
            "id": "5bd89899bda5c343749d00f0",
            "name": "marcio",
            "cpf": null,
            "phone": "11999999999",
            "email": "marcio@gmail.com",
            "birthday": "2018-10-30T17:44:57.834Z"
        },
        "user_detail": [
            {
                "value": 50
            },
            {
                "value": 50
            },
            {
                "value": 40
            },
            {
                "value": 20
            },
            {
                "value": 20
            },
            {
                "value": 50
            },
            {
                "value": 18
            },
            {
                "value": 20
            },
            {
                "value": 20
            },
            {
                "value": 10
            },
            {
                "value": 120
            },
            {
                "value": 50
            },
            {
                "value": 120
            },
            {
                "value": 20
            },
            {
                "value": 20
            },
            {
                "value": 25
            },
            {
                "value": 20
            },
            {
                "value": 20
            },
            {
                "value": 20
            },
            {
                "value": 10
            },
            {
                "value": 20
            },
            {
                "value": 20
            },
            {
                "value": 35
            },
            {
                "value": 20
            },
            {
                "value": 20
            }
        ]
    }

如何将所有字段相加value并显示该总和的结果与我的第一个 $group 的结果？

Answer 1

您可以 $sum对数组值使用聚合

db.user.aggregate([
  // $group stage
  { "$lookup": {
    "from": "schedule",
    "localField": "_id.phone",
    "foreignField": "customer.phone",
    "as": "user_detail"
  }},
  { "$project": {
    "total": { "$sum": "$user_detail.value" }
  }}
])