title: Return Only the Keys from Document Where the Query condition was True
body: <p>I'm having group of elements in MongoDB as given below:</p>
  
  <pre><code>{
      "_id": ObjectId("5942643ea2042e12245de00c"),
      "user": NumberInt(1),
      "name": {
          "value": "roy",
          "time": NumberInt(121)
      },
      "lname": {
          "value": "roy s",
          "time": NumberInt(122)
      },
      "sname": {
          "value": "roy 9",
          "time": NumberInt(123)
      }
  }
  </code></pre>
  
  <p>but when I execute the query below </p>
  
  <pre><code>db.temp.find({
      $or: [{
          'name.time': {
              $gte: 123
          }
      }, {
          'lname.time': {
              $gte: 123
          }
      }, {
          'sname.time': {
              $gte: 123
          }
      }]
  })
  </code></pre>
  
  <p>it is returning the whole document which is correct.</p>
  
  <p>Is there any way to fetch only specified object in which condition matched.Like in my document let condition within lname.time equl to 122 then only lname object will return rest will ignored.</p>