challenges_aggregation.diff

diff --git a/src/controllers/challenges.js b/src/controllers/challenges.js
index 9545f4a..6c74de5 100644
--- a/src/controllers/challenges.js
+++ b/src/controllers/challenges.js
@@ -105,20 +105,26 @@ api.csv = function(req, res, next) {
 
 api.getMember = function(req, res, next) {
   var cid = req.params.cid, uid = req.params.uid;
-  User.findById(uid)
-    .select('profile.name habits dailys todos rewards')
-    .exec(function(err, member){
+
+  User.aggregate([
+    {$match:{_id:uid}},
+    {$project:{'profile.name':1,habits:1,dailys:1,todos:1,rewards:1}},
+    {$unwind:"$habits"},
+      {$match:{"habits.challenge.id":cid}},
+      {$group:{_id:"$_id", "habits":{$push:"$habits"}}},
+    {$unwind:"$dailys"},
+      {$match:{"dailys.challenge.id":cid}},
+      {$group:{_id:"$_id", "dailys":{$push:"$dailys"}}},
+    {$unwind:"$todos"},
+      {$match:{"todos.challenge.id":cid}},
+      {$group:{_id:"$_id", "todos":{$push:"$todos"}}},
+    {$unwind:"$rewards"},
+      {$match:{"rewards.challenge.id":cid}},
+      {$group:{_id:"$_id", "rewards":{$push:"$rewards"}}}
+  ]).exec(function(err, member){
+      member = member[0];
       if(err) return next(err);
       if (!member) return res.json(404, {err: 'Member '+uid+' for challenge '+cid+' not found'});
-
-      // Prune un-related tasks. See http://goo.gl/9fnwei
-      // See http://stackoverflow.com/a/18546277/362790 for fix
-      _.each(['habits','dailys','todos', 'rewards'], function(type){
-        member[type] = _.filter(member[type], function(task){
-          return task.challenge && task.challenge.id && task.challenge.id == cid;
-        });
-      });
-
       res.json(member);
     })
 }