Question

给出一个包含以下文档的集合：

{
    "host" : "example.com",
    "ips" : [
        {
            "ip" : NumberLong("1111111111"),
            "timestamp" : NumberLong(1373970044)
        },
        {
            "ip" : NumberLong("2222222222"),
            "timestamp" : NumberLong(1234978746)
        }
    ]
}

我需要返回ip值为X的所有文档，但前提是X的关联时间戳是ips数组中的最高时间戳（因此上面的示例文档应不匹配搜索“2222222222”，因为不具有最新时间戳的IP。）

这是我第一次在MongoDB中做一些非常基本的东西，所以我能得到的最接近的是：

coll.aggregate（{$匹配：{ “ips.ip”：X}}，{$组：{ “_ ID”： “$主机”， “最大值”：{$最大： “$ ips.timestamp”}}}，{$排序：{ “ips.timestamp”： - 1}}）导致

这显然没有给我我正在寻找的东西，它返回任何ips.ip值为X.如果X的关联时间戳最高，我怎么才返回ip.ip为X的文件那个ips阵列？

Answer 1

如果Host是唯一的，则以下代码应该完成此任务。否则，您只需在分组操作中通过_id替换主机

coll.aggregate([
  {$unwind: "$ips"},
  {$project:{host:"$host",ip:"$ips.ip", ts:"$ips.timestamp"} },
  {$sort:{ts:1} },
  {$group: {_id: "$host", IPOfMaxTS:{$last: "$ip"}, ts:{$last: "$ts"} } }
])

我希望它有所帮助。

Answer 2

从mongo 3.4版本开始，您可以在聚合管道中使用$reduce

db.t64.aggregate([
    {$addFields : {ips : {$reduce : {
        input : "$ips", 
        initialValue : {timestamp : 0}, 
        in : {$cond: [{$gte : ["$$this.timestamp", "$$value.timestamp"]},"$$this", "$$value"]}}
    }}}
])

样品采集

> db.t64.findOne()
{
        "_id" : ObjectId("5c45e00f328877e101354d97"),
        "host" : "example.com",
        "ips" : [
                {
                        "ip" : NumberLong(1111111111),
                        "timestamp" : NumberLong(1373970044)
                },
                {
                        "ip" : NumberLong("2222222222"),
                        "timestamp" : NumberLong(1234978746)
                }
        ]
}

输出

> db.t64.aggregate([ {$addFields : {ips : {$reduce : { input : "$ips",  initialValue : {timestamp : 0},  in : {$cond: [{$gte : ["$$this.timestamp", "$$value.timestamp"]},"$$this", "$$value"]}} }}} ])
{ "_id" : ObjectId("5c45e00f328877e101354d97"), "host" : "example.com", "ips" : { "ip" : NumberLong(1111111111), "timestamp" : NumberLong(1373970044) } }

Answer 3

IN Simple Words ，如果您有 mongo查询响应，如下所示 - 并且您只需要来自 Array-＆gt;的最高值“日期”

{ "_id": "57ee5a708e117c754915a2a2", "TotalWishs": 3, "Events": [ "57f805c866bf62f12edb8024" ], "wish": [ "Cosmic Eldorado Mountain Bikes, 26-inch (Grey/White)", "Asics Men's Gel-Nimbus 18 Black, Snow and Fiery Red Running Shoes - 10 UK/India (45 EU) (11 US)", "Suunto Digital Black Dial Unisex Watch - SS018734000" ], "Date": [ "2017-02-13T00:00:00.000Z", "2017-03-05T00:00:00.000Z" ], "UserDetails": [ { "createdAt": "2016-09-30T12:28:32.773Z", "jeenesFriends": [ "57edf8a96ad8f6ff453a384a", "57ee516c8e117c754915a26b", "58a1644b6c91d2af783770b0", "57ef4631b97d81824cf54795" ], "userImage": "user_profile/Male.png", "email": "roopak@small-screen.com", "fullName": "Roopak Kapoor" } ], },

***然后你添加了

Latest_Wish_CreatedDate：{$ max：“$ Date”}，

如下所示 -

{ $project : { _id: 1, TotalWishs : 1 , wish:1 , Events:1, Wish_CreatedDate:1, Latest_Wish_CreatedDate: { $max: "$Date"}, } }

最终查询响应将低于

{ "_id": "57ee5a708e117c754915a2a2", "TotalWishs": 3, "Events": [ "57f805c866bf62f12edb8024" ], "wish": [ "Cosmic Eldorado Mountain Bikes, 26-inch (Grey/White)", "Asics Men's Gel-Nimbus 18 Black, Snow and Fiery Red Running Shoes - 10 UK/India (45 EU) (11 US)", "Suunto Digital Black Dial Unisex Watch - SS018734000" ], "Wish_CreatedDate": [ "2017-03-05T00:00:00.000Z", "2017-02-13T00:00:00.000Z" ], "UserDetails": [ { "createdAt": "2016-09-30T12:28:32.773Z", "jeenesFriends": [ "57edf8a96ad8f6ff453a384a", "57ee516c8e117c754915a26b", "58a1644b6c91d2af783770b0", "57ef4631b97d81824cf54795" ], "userImage": "user_profile/Male.png", "email": "roopak@small-screen.com", "fullName": "Roopak Kapoor" } ], "Latest_Wish_CreatedDate": "2017-03-05T00:00:00.000Z" },

MongoDB在文档数组中按最大值查找

3 个答案: