如何在MongoDB中计算数组重复元素

Anji 发表于 Dev

Anji

MongoDB中的数据具有以下准备聚合功能1

{"_id" : { "monthDate":"04-03-2020"}, "Job" : [ "Designer","Tester","Designer"]} 
{"_id" : { "monthDate":"14-03-2020"}, "Job" : [ "Designer","Tester","Tester"]} 
{"_id" : { "monthDate":"24-03-2020"}, "Job" : [ "Developer","Manager"]} 
{"_id" : { "monthDate":"25-03-2020"}, "Job" : [ "Developer","Developer","Developer"]}

我需要以下输出

{"_id" : { "monthDate":"04-03-2020"}, "Job" : [ "Designer":2,"Tester":1]} 
{"_id" : { "monthDate":"14-03-2020"}, "Job" : [ "Designer":1,"Tester":2]} 
{"_id" : { "monthDate":"24-03-2020"}, "Job" : [ "Developer":1,"Manager":1]} 
{"_id" : { "monthDate":"25-03-2020"}, "Job" : [ "Developer":3]}

土生的

你可以试试，

$setUnion从Job数组中获得唯一的数组
$map 从上述操作迭代唯一数组的循环
$filter从主Job数组中获取匹配标签，并$size从过滤器中获取匹配标签总数
$arrayToObject 将k（key）和v（value）格式转换为对象格式

db.collection.aggregate([
  {
    $addFields: {
      Job: {
        $arrayToObject: {
          $map: {
            input: { $setUnion: "$Job" },
            as: "j",
            in: {
              k: "$$j",
              v: {
                $size: {
                  $filter: {
                    input: "$Job",
                    cond: { $eq: ["$$this", "$$j"] }
                  }
                }
              }
            }
          }
        }
      }
    }
  }
])

操场

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