A map reduce function that counts the requests for each path on each day.

mongo-mapreduce.coffee

db.receipts.ensureIndex({issued_at: 1})

map = ->
  day = @issued_at;
  data = 
    count: 1
    paths: {}
  data.paths[@path] = {count:1}
  emit(day, data);

reduce = (key, values) ->
  result =
    count: 0,
    paths: {}
  values.forEach (value) ->
    result.count++
    for path of value["paths"]
      result.paths[path] ||= {count: 0}
      result.paths[path].count++
  result

stats = db.receipts.mapReduce(map, reduce,
  query:
    status: '200'
  sort:
    issued_at: 1
  out: 'daily_hits_by_path'
  limit: 3000
)

mongo-mapreduce.js

var map, reduce, stats;
db.receipts.ensureIndex({
  issued_at: 1
});
map = function() {
  var data, day;
  day = this.issued_at;
  data = {
    count: 1,
    paths: {}
  };
  data.paths[this.path] = {
    count: 1
  };
  return emit(day, data);
};
reduce = function(key, values) {
  var result;
  result = {
    count: 0,
    paths: {}
  };
  values.forEach(function(value) {
    var path, _base, _results;
    result.count++;
    _results = [];
    for (path in value["paths"]) {
      (_base = result.paths)[path] || (_base[path] = {
        count: 0
      });
      _results.push(result.paths[path].count++);
    }
    return _results;
  });
  return result;
};
stats = db.receipts.mapReduce(map, reduce, {
  query: {
    status: '200'
  },
  sort: {
    issued_at: 1
  },
  out: 'daily_hits_by_path',
  limit: 3000
});