title: How to get a child of a mongo collections by the key?
body: <p>I ve got a collection users that look like this :</p>
  
  <pre><code>{
  _id: myid,
  name : 'blabla',
  ia : {
         [0]-&gt; 'an id',
         [1]-&gt; 'a second id'
        }
  }
  </code></pre>
  
  <p>And i want to have only my first id of ia, so i tried something like that :</p>
  
  <pre><code>User.find({ _id: id, ia :{ key : indexia} }, ['ia']).populate('ia').run(rendu);
  </code></pre>
  
  <p>where id= myid, and indexia=0.</p>
  
  <p>If i don t put that part : " ia :{ key : indexia}" i get all my ia... but i want only one.</p>
  
  <p>Hope i was clear. 
  Thanks</p>