使用$总和的对象，猫鼬/ MongoDB的计算总价值

Question

我有这样的：

var actions = [ 
    project: 23123, 
    title: 'Change of windows 
    energySaving: { 
     electricity: { 
     lighting: 24324, 
     equipment: 23423, 
     fans: 234234, 
     distribution: 234324, 
     chiller: 234234, 
     other: 234324 
     }, 
     heating: { 
     ventilation: 234324, 
     shell: 23423, 
     tapWater: 23423 
     }, 
    } 
]); 

这是我的查询来获取从行动收集某些字段：

mongoose.model('Action').find({project: project._id}) 
    .select('title description energySaving') 

     .exec(function(err, actions){ 
     res.status(200).send(actions); 
    }); 
    }) 

相反获得整个“energySaving”财产，我想用一个“totalEnergySaving”来代替它，它是所有子对象的总和。是否有可能使用聚合来做到这一点？如果是这样，那可能是$sum功能。虽然不太确定。

Answer 1

由于具有任意字段名称，因此用当前模式设计实现聚合将非常困难。为了做到种类最多的查询和操作，你就需要重新设计你的架构来存储这样的数据：

{ 
    "_id" : ObjectId("54f46f18c36dcc206d0cec38"), 
    "project" : 23123, 
    "title" : "Change of windows", 
    "energySaving" : [ 
     { 
      "energy" : "electricity", 
      "type" : "lighting", 
      "value" : 24324 
     }, 
     { 
      "energy" : "electricity", 
      "type" : "equipment", 
      "value" : 24324 
     }, 
     { 
      "energy" : "electricity", 
      "type" : "fans", 
      "value" : 24324 
     }, 
     { 
      "energy" : "electricity", 
      "type" : "distribution", 
      "value" : 24324 
     }, 
     { 
      "energy" : "electricity", 
      "type" : "chiller", 
      "value" : 24324 
     }, 
     { 
      "energy" : "electricity", 
      "type" : "other", 
      "value" : 24324 
     }, 
     { 
      "energy" : "heating", 
      "type" : "ventilation", 
      "value" : 24324 
     }, 
     { 
      "energy" : "heating", 
      "type" : "shell", 
      "value" : 24324 
     }, 
     { 
      "energy" : "heating", 
      "type" : "tapWater", 
      "value" : 24324 
     } 
    ] 
} 

然后你就可以汇总得到最终title，description和totalEnergySaving如下：

db.collection.aggregate([ 
    { $unwind: "$energySaving" }, 
    { 
     $group: { 
      _id: { 
      title: '$title', 
      description: '$description' 
      }, 
      totalEnergySaving: { $sum: '$energySaving.value' } 
     } 
    }, 
    { 
     $project: { 
      _id: 0, 
      title: '$_id.title', 
      description: '$_id.description', 
      totalEnergySaving: 1 
     } 
    } 
]); 

结果：

{ 
    "result" : [ 
     { 
      "totalEnergySaving" : 218916, 
      "title" : "Change of windows", 
      "description" : "Detailed breakdown of energy savings" 
     } 
    ], 
    "ok" : 1 
}