如何在 mongo DB 中使用聚合进行多层计数细分？

Question

我有以下结构的文档。{  name: "John Doe",  City : "OK",  Prepaid: "Y"},{  name: "Jane Doe",  City : "CA",  Prepaid: "N"},{  name: "Jule Doe",  City : "OK",  Prepaid: "N"},{  name: "Jake Doe",  City : "OK",  Prepaid: "Y"}我想先根据城市对它进行分组，然后再对预付费进行分组，并获得每种预付费类型的单独计数。看起来与此类似的东西。{  City : OK  Count : {    "filter": prepaid,    "count": {      Y : 2      N: 1    }  }}{  City : CA  Count : {    "filter": prepaid,    "count": {      Y : 0      N: 1    }  }}我尝试基于多个字段进行聚合，它给了我文档的总数而不是故障。这是我为聚合管道尝试的内容：db.collection.aggregate([    {$match:matchquery    },{$group:{_id:{city: '$city', prepaid: '$prepaid' }, count:{$sum:1}    }}])

Answer 1

您可以运行$group两次以prepaid首先计数，然后您可以应用$arrayToObject来获取Y/N对象键：

db.collection.aggregate([

    {

        $group: {

            _id: { city: "$City", prepaid: "$Prepaid" },

            total: { $sum: 1 }

        }

    },

    {

        $grop: {

            _id: "$_id.city",

            Count: {

                $push: {

                    k: "$_id.prepaid", v: "$total"

                }

            }

        }

    },

    {

        $project: {

            _id: 0,

            city: "$_id",

            Count: { $mergeObjects: [ { filter: "prepaid" }, { count: { $arrayToObject: "$Count" } } ] }

        }

    }

])