text: var start = Date.now();
  db.test.group( { key: {"thousandth" : true },
                   cond: { "$and": [{ "num" : { "$gte" : 10000 } },
                                    { "num" : { "$lt" : 20000 } }]},
                   initial: { "total" : 0 },
                   reduce: function(obj, prev) { prev.total += 1; }
                 } ).forEach(function(){});
  var end = Date.now() - start;
  end;
  