MongoDB MapReduce - Emit one key/one value doesnt call reduce

Question

So i\'m new with mongodb and mapreduce in general and came across this "quirk" (or atleast in my mind a quirk)

Say I have objects in my collection like so:

Answer 1

Solution:

• added new field in map: single: 0
• in reduce change this field to: single: 1

• in finalize make checking for this field and make required actions

  $map = new MongoCode("function() {
      var value = {
          time: this.time,
          email_id: this.email_id,
          single: 0
      };
  
      emit(this.email, value);
  }");
  
  $reduce = new MongoCode("function(k, vals) {
  
      // make some need actions here
      return {
          time: vals[0].time,
          email_id: vals[0].email_id,
          single: 1
      };
  }");
  
  $finalize = new MongoCode("function(key, reducedVal) {
      if (reducedVal.single == 0) {
          reducedVal.time = 11111;
      }
      return reducedVal;
  };");