小编dev*_*ull的帖子

我有一个看起来像这样的文件:

{
    "_id" : ObjectId("527a6b7c24a8874c078b9d10"),
    "day" : 6,
    "hour" : 15,
    "hourlyLocations" : [
        {
            "countryName" : "Spain",
            "countryCode" : "ES",
            "cityName" : "Madrid",
            "latitude" : 40,
            "longitude" : -4
        },
        {
            "countryName" : "United Kingdom",
            "countryCode" : "GB",
            "cityName" : "Soest",
            "latitude" : 51.5,
            "longitude" : -0.13
        }
    ],
    "minute" : 18,
    "month" : 11,
    "year" : 2013
}

"hourlyLocations"是一系列嵌入式文档(为简洁起见,这里只显示了两个).

我正在尝试运行一个聚合,它将返回每个国家,该国家的所有城市(一次)和每个城市的实例数量.

这是我到目前为止所得到的:

db.hourly.aggregate(
[
    { "$project" : { "hourly" : "$hourlyLocations" } },
    { "$unwind" : "$hourly" },
    { …

我有以下查询:

db.listener.aggregate(
[
    { "$match" : { "location.countryName" : "Italy" } },
    { "$project" : { "location" : "$location"} },
    { "$group" : { "_id" : { "country": "$location.countryName", "city": "$location.cityName" }, "count" : { "$sum" : 1 }, "co-ords" : { "$addToSet" : { "lat" : "$location.latitude", "long" : "$location.longitude" } } } },
    { "$group" : { "_id" : "$_id.country", "cities" : { "$push" : { "city" : "$_id.city", "count" : "$count", "co-ords" : "$co-ords" } } } …