title: Detect objects to be deleted from Realm database
body: <p>In my project I'm using Realm for storing data from API.
  Before updating objects to Realm I'd like to check which objects are new (doesn't exist in database) and which objects should be deleted (exist in database, but don't exist in API response).</p>
  
  <p>For checking new objects I'm iterating through API response and using simple Realm query to check which object is new</p>
  
  <pre><code>for(Follower follower: results.data){
        Follower followerFromDb = realm.where(Follower.class).equalTo("id", follower.id).findFirst();
          if(followerFromDb == null){
              Log.d("REALM", "Object is not in the DB");
          }
  }
  </code></pre>
  
  <p>My problem is - how to efficiently check which objects should be deleted from the database.</p>