Mongodb MapReduce示例1个
Map:
[java script]
map=function(){emit(this.classid,1)}
function () {
emit(this.classid, 1);
}
Reduce:
[java script]
reduce=function(key,values){
var x = 0;
values.forEach(function(v){x+=v});
return x;
}
执行：
[java script]
result=db.runCommand({
mapreduce:"students",
map:map,
reduce:reduce,
out:"students_result"
});