如何在对象内部排序并减去MongoDB中对象内部的值

Posted 2023-03-11

【中文标题】如何在对象内部排序并减去MongoDB中对象内部的值

【英文标题】：how to sort inside the object and subtract the values inside the objects in MongoDB

【发布时间】：2021-10-24 09:52:37

【问题描述】：

输入文件

  "data": 
    "2021-05-05": 
      "12": 2.1,
      "15": 0.2,
      "06": 2.6,
      "09": 2.2
    ,
    "2021-05-06": 
      "12": 2.1,
      "15": 0.2,
      "06": 2,
      "09": 1.7
    

中间步骤数据objects 将与键连接并按时间排序。

  "data": 
    "2021-05-05": 
      "2021-05-05T06:00:00:0Z": 2.6,
      "2021-05-05T09:00:00:0Z": 2.2,
      "2021-05-05T12:00:00:0Z": 2.1,
      "2021-05-05T15:00:00:0Z": 0.2

    ,
    "2021-05-06": 
      "2021-05-06T12:00:00:0Z": 2.1,
    

排序后。下一步将是。 Subtract 从value_last - value_first 相对于时间。

输出文档

Document 1

  "data": 
      "time_first" : "2021-05-05T06:00:00:0Z",
      "value_first": 2.6,
      "time_last": "2021-05-05T15:00:00:0Z"
      "value_last": "0.2",
      "difference_value_last-value_first" : -0.4

    

Document 2 如果只包含一个值，则上个月的value_last成为下一个文档的value_first 。

    "data": 
      "time_first" : "2021-05-05T15:00:00:0Z",
      "value_first": 0.2,
      "time_last":  "2021-05-06T12:00:00:0Z",
      "value_last": : 2.1 ,
      "difference_value_last-value_first" : 1.9
    

【参考方案1】：

你可以使用聚合

$objectToArray 把对象变成一个数组，所以我们可以得到键：值对，它定义了名称“k”，有助于获取数据 $unwind 解构数组 $sort 按条件排序 $group 查找我们排序的第一个和最后一个元素 $concat 拼接字符串日期时间字符串

这里是代码

db.collection.aggregate([
    $project:  data:  "$objectToArray": "$data  ,
  
    $project: 
      data: 
        $map: 
          input: "$data",
          in: 
            "dk": "$$this.k",
            "dv":  "$objectToArray": "$$this.v" 
          
        
      
    
  ,
   "$unwind": "$data" ,
   $unwind: "$data.dv" ,
  
    $sort: 
      "data.dk": -1,
      "data.dv.v": -1
    
  ,
  
    $group: 
      _id: "$data.dk",
      firstData:  $first: "$data.dv"  ,
      lastData:  $last: "$data.dv" 
    
  ,
  
    $project: 
      "time_first": 
        $concat: [ "$_id", "T", "$firstData.k", ":00:00:0Z" ]
      ,
      "time_last": 
        $concat: [ "$_id", "T", "$lastData.k", ":00:00:0Z" ]
      ,
      "value_first": "$firstData.v",
      "value_last": "$lastData.v",
      "difference_value_last-value_first": 
        "$subtract": [ "$lastData.v", "$firstData.v" ]
      
    
  
])

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