[Rails] Re: How to map/reduce two MongoDB collections

Ruby on Rails Friday, December 23, 2011

hi all,


After continuous 10 hours work i fixed it out. below is the code which i written in challenge model.

def self.task_score_map
    <<-MAP
      function() {
        this.tasks.forEach(function(aTask) {
          emit(aTask.score, {score: aTask.score});
        });
      }
    MAP
  end
  
  def self.task_score_reduce
    <<-REDUCE
      function(key, values) {
         var sum = 0;
         values.forEach(function(aScore) {
            sum += parseInt(aScore.score);
        });
        return sum;
        }
    REDUCE
  end
  
  def self.task_score_build(opts)
    self.collection.map_reduce(self.task_score_map, self.task_score_reduce, opts)
  end
  
  def self.task_score(opts={}) 
    hash = opts.merge({ 
      :out    => {:inline => true}, 
      :raw    => true 
    }) 
    self.task_score_build(hash).find() 
  end

and this is result

#<Enumerator: {"results"=>[{"_id"=>"10", "value"=>{"score"=>"10"}}, {"_id"=>"11", "value"=>{"score"=>"11"}}, {"_id"=>"5", "value"=>30.0}, {"_id"=>"6", "value"=>{"score"=>"6"}}, {"_id"=>"7", "value"=>{"score"=>"7"}}, {"_id"=>"8", "value"=>{"score"=>"8"}}, {"_id"=>"9", "value"=>{"score"=>"9"}}], "timeMillis"=>0, "counts"=>{"input"=>6, "emit"=>12, "reduce"=>1, "output"=>7}, "ok"=>1.0}:find>

i m sorting this a/c to score. but  i need a/c to user_id. here user_id belongs to challenge model.

"_id" : ObjectId("4ef1a6a454b53001a4000067"),
  "user_id" : "100002573213371",
  "title" : "social who wins",
  "description" : "social who wins",
  "updated_at" : new Date("Wed, 21 Dec 2011 14:58:04 GMT +05:30"),
  "created_at" : new Date("Wed, 21 Dec 2011 14:58:04 GMT +05:30"),
  "tasks" : [{
      "is_complete" : 0,
      "score_by" : "Check box:1 for checking off the task",
      "score" : "5",
      "name" : "task no 1",
      "_id" : ObjectId("4ef1a6a454b53001a4000068")
    }, {
      "is_complete" : 0,
      "score_by" : "Self-report number",
      "score" : "6",
      "name" : "task no 2",
      "_id" : ObjectId("4ef1a6a454b53001a4000069")
    }],
}

i need to pass user_id instead of score.

def self.task_score_map
    <<-MAP
      function() {
        this.tasks.forEach(function(aTask) {
          emit(this.user_id, {score: aTask.score});
        });
      }
    MAP
  end 

any idea...............

On 23 December 2011 11:38, Pravin Mishra <diatm.pravin.it.07.27@gmail.com> wrote:
Hi Guy's,

I am new to map / reduce and trying to figure out a way to collect the following data using map / reduce instead doing it my (slow) application logic:

I have a collection 'challenge' with a 1:n relation to a collection 'tasks'. Now I'd like to receive an array of results that gives top five heightest scored challenge.

For map I tried something like:

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


and reduce:

reduce = function (key, score) {
  var sum = 0;
  score.forEach(function(doc){ sum += 1; });
  return { count:sum };
}

I fired this against my tasks collection:

var mr = db.tasks.mapReduce(map, reduce, { out: "results" });
But I get crucial results when querying:

db[mr.result].find();
I am using Mongoid on Rails and am completely lost with it. Can someone point me into the right direction?

my data something  like this

/* 13 */
{
  "_id" : ObjectId("4ef1a6a454b53001a4000067"),
  "user_id" : "100002573213371",
  "title" : "social who wins",
  "description" : "social who wins",
  "updated_at" : new Date("Wed, 21 Dec 2011 14:58:04 GMT +05:30"),
  "created_at" : new Date("Wed, 21 Dec 2011 14:58:04 GMT +05:30"),
  "tasks" : [{
      "is_complete" : 0,
      "score_by" : "Check box:1 for checking off the task",
      "score" : "5",
      "name" : "task no 1",
      "_id" : ObjectId("4ef1a6a454b53001a4000068")
    }, {
      "is_complete" : 0,
      "score_by" : "Self-report number",
      "score" : "6",
      "name" : "task no 2",
      "_id" : ObjectId("4ef1a6a454b53001a4000069")
    }],
}

/* 14 */
{
  "_id" : ObjectId("4ef1a6a454b53001a400006d"),
  "canCompleteBeforeTasks" : true,
  "challenge_id" : ObjectId("4ef1a6a454b53001a4000067"),
  "created_at" : new Date("Wed, 21 Dec 2011 14:58:04 GMT +05:30"),
  "description" : "social who wins",
  "tasks" : [{
      "is_complete" : 0,
      "score_by" : "Check box:1 for checking off the task",
      "score" : "5",
      "name" : "task no 1",
      "_id" : ObjectId("4ef1a6a454b53001a400006e")
    }, {
      "is_complete" : 0,
      "score_by" : "Self-report number",
      "score" : "7",
      "name" : "task no 2",
      "_id" : ObjectId("4ef1a6a454b53001a400006f")
    }],
  "title" : "social who wins",
  "updated_at" : new Date("Wed, 21 Dec 2011 14:58:04 GMT +05:30"),
  "user_id" : "100003135115833"
}

/* 15 */
{
  "_id" : ObjectId("4ef1a6a454b53001a4000073"),
  "challenge_id" : ObjectId("4ef1a6a454b53001a4000067"),
  "created_at" : new Date("Wed, 21 Dec 2011 14:58:04 GMT +05:30"),
  "description" : "social who wins",
  "tasks" : [{
      "is_complete" : 0,
      "score_by" : "Check box:1 for checking off the task",
      "score" : "5",
      "name" : "task no 1",
      "_id" : ObjectId("4ef1a6a454b53001a4000074")
    }, {
      "is_complete" : 0,
      "score_by" : "Self-report number",
      "score" : "8",
      "name" : "task no 2",
      "_id" : ObjectId("4ef1a6a454b53001a4000075")
    }],
  "title" : "social who wins",
  "updated_at" : new Date("Wed, 21 Dec 2011 14:58:04 GMT +05:30"),
  "user_id" : "100003174704960"
}


Thx in advance.



++++++++++++++++++
Pravin Mishra


--
You received this message because you are subscribed to the Google Groups "Ruby on Rails: Talk" group.
To post to this group, send email to rubyonrails-talk@googlegroups.com.
To unsubscribe from this group, send email to rubyonrails-talk+unsubscribe@googlegroups.com.
For more options, visit this group at http://groups.google.com/group/rubyonrails-talk?hl=en.

Posted by Ruby on Rails at 6:16 AM

No comments:

Post a Comment

Subscribe to: Post Comments (Atom)