mongo 4.0以下版本 类型转换

1.文档格式

 "Values" : [ 
        {
            "key" : "姓名",
            "value" : "jenny"
        }, 
        {
            "key" : "年龄",
            "value" : "20"
        }]

2.查询

将values字段平铺到根。并将年龄字段值转换成int。按姓名降序

db.getCollection('Users').aggregate([
{$addFields: {
        ValueObj: {
          $arrayToObject: {
            $map: {
              input: "$Values",
              as: "field",
              in: {$cond:[{$eq:["$$field.key","年龄"]},["$$field.key", NumberInt("$$field.value")],["$$field.key", "$$field.value"]]}
            }
          }
        }
      }
  },
  {$addFields:{"ValueObj.Values":"$Values"}},
  {$replaceRoot:{newRoot:"$ValueObj"}},
  {$sort:{"姓名":-1}},
 
])

3.结果

"姓名" : "jenny",
    "年龄" : 20,
    "Values" : [ 

        {
            "key" : "姓名",
            "value" : "jenny"
        }, 
        {
            "key" : "年龄",
            "value" : "20" }]