Runs a map/reduce across a MongoDB data set.

mongodb-mapreduce.js

var end = new Date();
var start = new Date();
start.setTime(start.getTime()-300000); //5 minutes prior

// print dates in the format YYYY-MM-DD HH:MM:SS so we can do Mysql LOAD IN FILE on them
// Note that in JS the month portion of the Date constructor is 0-indexed
var my_s = start.getFullYear() + "-" + (start.getMonth()+1) + "-" + start.getDate() + " " + start.getHours() + ":" + start.getMinutes() + ":" + start.getSeconds();
var my_e = end.getFullYear() + "-" + (end.getMonth()+1) + "-" + end.getDate() + " " + end.getHours() + ":" + end.getMinutes() + ":" + end.getSeconds();
print(my_s + ',' + my_e);

map = function() {
  emit({aid:this.aid, type:this.type}, {count: 1}); 
}

reduce = function (key, values) {
  var count = 0;
  values.forEach(function (v) {count += v.count;});
  return {count:count};
}

db.realtime.mapReduce(map, reduce, {query : {ts: {$gte: start, $lt: end}}, out: "rtresults"});

var rtcount = db.rtresults.count();
print('Result count: ' + tojson(rtcount));