Question

我在mongoDB中有以下集合

{ _id, startTime, duration }

所以基本的想法是摄像机会寻找人，一旦它检测到一个人就会保存startTime，一旦一个人消失，就可以节省持续时间。因此，该实体基本上说“一个人出现在X时间，并且在摄像机范围内为Y毫秒”。 startTime和duration都是数值。

所以，我想执行各种查询，例如： 1.给我每月/每年的人数 2.给我一个月的人数，持续时间>值为5000ms

等

我对MongoDB相当新，但是我对聚合框架有点麻烦，所以如果有人给我一个如何进行上述查询的想法，我会很感激，以便得到某种排序先发制人。

编辑：

好的，我做过几次尝试，但没有运气。现在我的对象有这样的形式：

{
  "_id" : ObjectId("52de407c75895eaf5ea99715"),
  "startTime" : "new Date('02 01 2011 08:36:54')",
  "duration" : 27000
}

我正在尝试此查询：

 db.collection.aggregate(
        {$project : {
             year : {$year : "$startTime"}

        }},
        {$group : {
             _id : {year : "$year"}, 
             count : {$sum : 1}
        }}
    )

但我得到以下例外：

Error occurred in performing aggregation
Command 'aggregate' failed: exception: can't convert from BSON type String to Date (response: { "errmsg" : "exception: can't convert from BSON type String to Date", "code" : 16006, "ok" : 0.0 })
Type: MongoDB.Driver.MongoCommandException
Stack:    at MongoDB.Driver.Operations.CommandOperation`1.Execute(MongoConnection connection)
   at MongoDB.Driver.MongoCollection.RunCommandAs[TCommandResult](IMongoCommand command, IBsonSerializer resultSerializer, IBsonSerializationOptions resultSerializationOptions)
   at MongoDB.Driver.MongoCollection.RunCommandAs[TCommandResult](IMongoCommand command)
   at MongoDB.Driver.MongoCollection.Aggregate(IEnumerable`1 operations)
   at MangoUI.ComAggregate.kRemove_Click(Object sender, EventArgs e)
Inputs:: 
Command:  aggregate
Ok:       False
ErrorMsg: exception: can't convert from BSON type String to Date
Request:  { "aggregate" : "person", "pipeline" : [{ "$project" : { "year" : { "$year" : "$startTime" } } }, { "$group" : { "_id" : { "year" : "$year" }, "count" : { "$sum" : 1 } } }] }
Response: { "errmsg" : "exception: can't convert from BSON type String to Date", "code" : 16006, "ok" : 0.0 }

Answer 1

您可以使用聚合框架来完成它们。

给我每月/每年的人数

db.collection.aggregate(
    {$project : {
         year : {$year : "$startTime"}, 
         month : {$month : "$startTime"}
    }},
    {$group : {
         _id : {year : "$year", month : "$month"}, 
         count : {$sum : 1}
    }}
)

给我一个月的人数，持续时间＆gt;值为5000ms

db.collection.aggregate(
    {$project : {
         year : {$year : "$startTime"}, 
         month : {$month : "$startTime"}, 
         duration: {$cond: [{$gt: ['$duration', 5000]}, 1, 0]}
    }},
    {$group : {
         _id : {year : "$year",month : "$month"}, 
         duration : {$sum : "$duration"}
    }}
)

有关详细信息，请查看Aggregation Framework.

Answer 2

请参考http://docs.mongodb.org/manual/reference/bson-types/#document-bson-type-date

的MongoDB兼容数据格式

以下是测试聚合的方法。

 rs1:PRIMARY> 
rs1:PRIMARY> db.dbversitycol.insert({ "_id" : "1", "LastUpdatedOn" : new Date() , "company" : "microsoft" })
rs1:PRIMARY> db.dbversitycol.insert({ "_id" : "2", "LastUpdatedOn" : new Date() , "company" : "google" })
rs1:PRIMARY> db.dbversitycol.insert({ "_id" : "3", "LastUpdatedOn" : new Date() , "company" : "ibm" })
rs1:PRIMARY> db.dbversitycol.insert({ "_id" : "4", "LastUpdatedOn" : new Date() , "company" : "cisco" })
rs1:PRIMARY> db.dbversitycol.insert({ "_id" : "5", "LastUpdatedOn" : new Date() , "company" : "dbversity.com" })
rs1:PRIMARY> 
rs1:PRIMARY> db.dbversitycol.find()
{ "_id" : "1", "LastUpdatedOn" : ISODate("2014-11-28T13:09:13.203Z"), "company" : "microsoft" }
{ "_id" : "2", "LastUpdatedOn" : ISODate("2014-11-28T13:09:13.207Z"), "company" : "google" }
{ "_id" : "3", "LastUpdatedOn" : ISODate("2014-11-28T13:09:13.210Z"), "company" : "ibm" }
{ "_id" : "4", "LastUpdatedOn" : ISODate("2014-11-28T13:09:13.213Z"), "company" : "cisco" }
{ "_id" : "5", "LastUpdatedOn" : ISODate("2014-11-28T13:09:14.035Z"), "company" : "dbversity.com" }
rs1:PRIMARY> 
rs1:PRIMARY> 
rs1:PRIMARY> db.dbversitycol.aggregate(
... {
...     "$project" :
...     {
...        _id : 0,
...        "datePartDay" : {"$concat" : [
...            {"$substr" : [{"$dayOfMonth" : "$LastUpdatedOn"}, 0, 2]}, "-",
...            {"$substr" : [{"$month" : "$LastUpdatedOn"}, 0, 2]}, "-",
...            {"$substr" : [{"$year" : "$LastUpdatedOn"}, 0, 4]}
...       ] }
...     }
... },
... { "$group" :
...     { "_id" : "$datePartDay", "Count" : { "$sum" : 1 } }
...     }
... )
{ "result" : [ { "_id" : "28-11-2014", "Count" : 5 } ], "ok" : 1 }
rs1:PRIMARY> 
rs1:PRIMARY> 



rs1:PRIMARY> db.dbversitycol.aggregate(
...     {$project : {
...          year : {$year : "$LastUpdatedOn"}, 
...          month : {$month : "$LastUpdatedOn"}
...     }},
...     {$group : {
...          _id : {year : "$year", month : "$month"}, 
...          count : {$sum : 1}
...     }}
... )
{
        "result" : [
                {
                        "_id" : {
                                "year" : 2014,
                                "month" : 11
                        },
                        "count" : 5
                }
        ],
        "ok" : 1
}
rs1:PRIMARY>

您可以在http://www.dbversity.com/

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