mongodb map reduce

最新推荐文章于 2024-07-25 11:48:36 发布

原创最新推荐文章于 2024-07-25 11:48:36 发布 · 662 阅读

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本文展示了如何使用MongoDB中的MapReduce功能来汇总薪资数据。通过具体的命令行操作步骤，演示了数据插入、MapReduce函数定义及执行过程，并最终展示聚合后的结果。

ubuntu@ubuntu:~$ mongo
MongoDB shell version: 2.4.9
connecting to: test
> db.salary.insert({name:"tom",salary:98})
> db.salary.insert({name:"tom",salary:96})
> db.salary.insert({name:"jerry",salary:86})
> db.salary.insert({name:"jerry",salary:88})
> db.salary.find()
{ "_id" : ObjectId("532be543edb9e06960e550b3"), "name" : "tom", "salary" : 98 }
{ "_id" : ObjectId("532be54eedb9e06960e550b4"), "name" : "tom", "salary" : 96 }
{ "_id" : ObjectId("532be559edb9e06960e550b5"), "name" : "jerry", "salary" : 86 }
{ "_id" : ObjectId("532be55eedb9e06960e550b6"), "name" : "jerry", "salary" : 88 }
> 
> var map = function(){emit(this.name,this.salary);}
> var reduce = function(key,values){return Array.sum(values)}
> db.salary.mapReduce(map,reduce,options)
Fri Mar 21 17:30:54.645 ReferenceError: options is not defined
> db.salary.mapReduce(map,reduce,{out:"salary_"})
{
        "result" : "salary_",
        "timeMillis" : 168,
        "counts" : {
                "input" : 4,
                "emit" : 4,
                "reduce" : 2,
                "output" : 2
        },
        "ok" : 1,
}
> db.salary_find()
Fri Mar 21 17:31:59.195 TypeError: Property 'salary_find' of object test is not a function
> db.salary_.find()
{ "_id" : "jerry", "value" : 174 }
{ "_id" : "tom", "value" : 194 }
>