MongoDB : Calculating wrongly in mapReduce -

this collection named logins

db.logins.find().pretty()         "cust_id" : "testuser",        "created_at" : "2011-03-11 10:31:02.765"        "cust_id" : "testuser",       "created_at" : "2011-03-11 10:31:02.765" 

i trying find out logins of each user based on date

i tried way

var m = function() {     var aux = this.created_at.indexof(' ');     emit({cust:this.cust_id,daterr:this.created_at.substring(0,aux)},1); }  var r = function(k, values) {   var l = values.length;   var r = 0;   var i;   (i=0; i<l; i++) {     r+=l;   }   return r; }   q = function() {         var query = {"created_at": {$lt: "2013-04-30 11:19:52.587"}}         return query;     }  db.logins.mapreduce(m, r, { query : q(), out :  "userlogincountmonthly" }); 

i getting following output

db.userlogincountmonthly.find().pretty()  { "_id" : { "cust" : "testuser", "daterr" : "2011-03-11" }, "value" : 4 } 

what see value must 2 , shown 4

could please tell me why displaying wrong ??

i may totally off in since i've never used mongodb's mapreduce , i'm not quite sure you're trying achieve in reduce, looks wrong;

var l = values.length; var r = 0; var i; (i=0; i<l; i++) {   r+=l; } return r; 

if values.length 2, loop twice, each time adding 2, returning 4.

as far can see since want count, simple return values.length make more sense reduce function.