laravel mongodb中按日期分组

我用的是mongo和laravel。 我在一段时间内获取数据，通常是30天。我想按天对数据进行分组。我尝试了

$project

$dayOfMonth

并按

天

分组，但它将它们按月份中的天进行分组，并且我希望按时段中的天进行排序。 有办法吗

[
     '$match' => [
           "created_at" => [
               '$gte' => new \MongoDB\BSON\UTCDateTime($thisMonth),
                        ]
                    ],
                ],
                    [
      '$project' => [
              'day' => [
              '$dayOfMonth' => [
              'date' => '$created_at',
               ]
         ],
      ]

 ],
 [
      '$group' => [
                 '_id' => '$day',
                  'count' => ['$sum' => 1],
          ],

 ],

样本：

  {#940
  flag::STD_PROP_LIST: false
  flag::ARRAY_AS_PROPS: true
  iteratorClass: "ArrayIterator"
  storage: array:16 [
    "_id" => ObjectId {#933
      +"oid": "5b2ff00e35826377be16ff82"
    }
    "orderNumber" => "10000"
    "userName" => "dGFraHRlLTkwMDQ2NDcyOJRbugaZlHWdMR+nCNzaUfY=" 
    "updated_at" => UTCDateTime {#938
      +"milliseconds": "1529868539000"
    }
    "created_at" => UTCDateTime {#939
      +"milliseconds": "1529868302000"
    }
  ]
}

您可以使用根据所需格式将日期对象转换为字符串

[ "$match" => [
  "created_at" => [ '$gte' => new \MongoDB\BSON\UTCDateTime($thisMonth) ]
]],
[ "$group" => [
  "_id" => [ "$dateToString" => [ "format" => "%Y-%m-%d", "date" => "$created_at" ] ],
  "count" => [ "$sum" => 1 ]
]]

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你能邮寄一些样品吗collection@AnthonyWinzlet补充