Mongodb Atlas警报：查询定位：已扫描的对象/已返回已超过1000

Question

汇总查询：

 db.events.aggregate([
        {$match: { "generated_at": {
            "$gte": new Date(2017, 0, 1),
            "$lte": new Date(2017, 3, 1)
        }, game_id: ObjectId("59de213e9c43f70001c29bef"), event_type: "session"}},
        {$project: { generated_at: "$generated_at", user_device_id: "$user_device_id", 
            avg_user_session_duration: {
                $avg: "$session_duration"
            }
        }},
        {$group: { _id: {day: { $dayOfMonth: "$generated_at"}, month: {$month: "$generated_at"},  year: { $year: "$generated_at"} }, 
            avg_session_duration_per_user: {
                $avg: "$avg_user_session_duration"
            }
        }},
        {$sort: {"_id.year": 1, "_id.month": 1, "_id.day": 1}}
    ])

索引：

 {
    "v" : 2,
    "key" : {
        "generated_at" : 1,
        "game_id" : 1,
        "event_type" : 1,
        "impression_type" : 1,
        "source_name" : 1
    },
    "name" : "generated_at_1_game_id_1_event_type_1_impression_type_1_source_name_1",
    "ns" : "analyticsdb.events"
}

我有如上所述的聚合查询，它适用于小数据集，但我有超过1000万个大小超过2GB的文档。我正在使用mongo atlas M10实例。我从mongo地图册得到这个警报。 shell也一直在等待查询结果，但从不给出任何响应。