Map Reduce Mongodb Node JS本机驱动程序

Question

我正在使用Map reduce函数处理Mongodb本机驱动程序。基本上，我有一个mediaId作为密钥，想计算每个mediaId加载和启动的媒体数量。所以我所做的是：

  var map = function(){
        emit(this.media.id, {
            count: 1,
            played: 0,
            ph: this.project.id,
            title: this.media.title,
            media: this.media.id,
            origin: this.origin,
            thumbnail: this.media.thumbnail,
            mediaDuration: this.media.mediaDuration,
            state: this.state
        });
    };
    var reduce = function(k, vals) {
        result = {
            count: 0,
            played: 0,
            ph: '',
            title: '',
            media: '',
            origin: '',
            thumbnail: '',
            mediaDuration: 0,
            state: ''
        };
        vals.forEach(function(doc){
            result.count += doc.count;
            result.ph = doc.ph;
            result.title = doc.title;
            result.media = doc.media;
            result.thumbnail = doc.thumbnail;
            result.mediaDuration = doc.mediaDuration;
            result.state = doc.state;
            result.origin = doc.origin;
            if(doc.state === "started") {
                result.played += 1;
            }
        });
        return result;
    };

在我的测试集合中，我有两个不同的mediaId。一个有553个对象，另一个只有1个对象。我已经把所有的推杆都放在"开始"状态来测试这一点，所以基本上计数的数量应该等于比赛的数量。当我运行Map/Reduce函数时，它会返回给我（我使用了mongodb本地驱动程序的"toArray"函数）：

[ { _id: '12398asdsa9802193810asd120',
value: 
 { count: 1,
   played: 0,
   ph: '123213ased12231',
   title: 'xxxxxxxxxxxxxxxxxxxxxxxxxxx',
   media: '1xxxxxxxxxxxxxxxxxxxxxxxxxxx1',
   origin: 'http://www.google.com',
   thumbnail: 'http://cache.ohinternet.com/images/0/0e/Forever_Alone.png',
   mediaDuration: 12321321,
   state: 'started' } },
{ _id: '2c9f94b42f5b5114012f5b92ea430066',
value: 
 { count: 553,
   played: 155,
   ph: '316',
   title: 'xxxxxxxxxxxxxxxxxxxxxxxxxxx',
   media: '2xxxxxxxxxxxxxxxxxxxxxxxxxxx2',
   origin: 'http://localhost:9000/views/index.html',
   thumbnail: null,
   mediaDuration: null,
   state: 'started' } } ]

我似乎只有一个reduce函数没有调用的对象（我对另一个有100多个mediaId的集合进行了一些测试，结果完全相同。有人知道这是怎么回事吗？

非常感谢您抽出时间，干杯

Answer 1

我在某种程度上解决了"问题"。我在Map函数上做了过滤，而不是在Reduce函数上。类似这样的东西：

var map = function(){
    if(this.media.state==="started") {
       var played = 1;
}else{var played = 0;}
    emit(this.media.id, {
        count: 1,
        played: played,
        ph: this.project.id,
        title: this.media.title,
        media: this.media.id,
        origin: this.origin,
        thumbnail: this.media.thumbnail,
        mediaDuration: this.media.mediaDuration,
        state: this.state
    });
};

希望它能帮助任何有同样"问题"的人