MongoDB MapReduce 的示例。

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// JavaScript source code
db.runCommand({
    mapreduce: "page",
    map: function Map() {
 
 
        emit(
            this.title,                 // how to group
            { name: this.name } // associated data point (document)
        );
 
 
    },
    reduce: function Reduce(key, values) {
        //reduce用来处理group出来是多条数据的地方
        /*
     
        var reduced = {count:0, age:0}; // initialize a doc (same format as emitted value)
     
        values.forEach(function(val) {
            reduced.age   += val.age;   // reduce logic
            reduced.count += val.count;
        });
     
        return reduced;
         
        */
 
        return values[0];
    },
    finalize: function Finalize(key, reduced) {
        //finalize用来处理group出来是一条数据的地方
        return reduced;
    },
    out: { reduce: "test", db: "testdb" }
});

 

posted @   iDEAAM  阅读(313)  评论(0编辑  收藏  举报
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