如何在 mongodb 的数组中合并具有相同键的对象？

Posted 2023-03-11

【中文标题】如何在 mongodb 的数组中合并具有相同键的对象？

【英文标题】：How can I merge objects with the same key in an array in mongodb?

【发布时间】：2021-12-18 11:06:36

【问题描述】：

我使用 mongodb 的聚合导出了以下数据。

    "first_count": 2,
    "second_count": 1,
    "third_count": 2,
    "test_count": 2,
    "sido": "대구",
    "guguns": [
        
            "gugun": "남시",
            "first_count": 1,
            "second_count": 1,
            "third_count": 1
        ,
        
            "gugun": "부천군",
            "first_count": 1,
            "second_count": 0,
            "third_count": 1
        ,
        
            "gugun": "남시",
            "test_count": 1
        ,
        
            "gugun": "부천군",
            "test_count": 1
        
    ]

这是合并两个方面数据的结果。但我想要的结果是：

    "first_count": 2,
    "second_count": 1,
    "third_count": 2,
    "test_count": 2,
    "sido": "대구",
    "guguns": [
        
            "gugun": "남시",
            "first_count": 1,
            "second_count": 1,
            "third_count": 1,
            "test_count": 1
        ,
        
            "gugun": "부천군",
            "first_count": 1,
            "second_count": 0,
            "third_count": 1,
            "test_count": 1
        
    ]

guguns.gugun如何将相同的值合二为一？ 如果可能的话，我想使用 mongodb 聚合来处理它。

【参考方案1】：

$unwind 解构 guguns 数组 $mergeObjects 将guguns 的当前对象与其他对象合并 $group by _id 和 guguns.gugun 属性并获取必填字段第一个值和 guguns 合并对象 $group 仅由_id 获取所需字段的第一个值并构造guguns 对象的数组

db.collection.aggregate([
   $unwind: "$guguns" ,
  
    $group: 
      _id: 
        _id: "$_id",
        gugun: "$guguns.gugun"
      ,
      first_count:  $first: "$first_count" ,
      second_count:  $first: "$second_count" ,
      third_count:  $first: "$third_count" ,
      test_count:  $first: "$test_count" ,
      sido:  $first: "$sido" ,
      guguns:  $mergeObjects: "$guguns" 
    
  ,
  
    $group: 
      _id: "$_id._id",
      first_count:  $first: "$first_count" ,
      second_count:  $first: "$second_count" ,
      third_count:  $first: "$third_count" ,
      test_count:  $first: "$test_count" ,
      sido:  $first: "$sido" ,
      guguns:  $push: "$guguns" 
    
  
])

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