title: Parse js sdk, How do you query many to many in document DB?
body: <p>In the Parse js guide it says:</p>
  
  <blockquote>
    <p>For example, a User may have many Posts that she might like. In this case, you can store the set of Posts that a User likes using relation. In order to add a Post to the “likes” list of the User, you can do:</p>
    
    <p><code>var user = Parse.User.current();
    var relation = user.relation("likes");
    relation.add(post);
    user.save();</code></p>
  </blockquote>
  
  <p>My use case is actually this exact setup.  We have Users and they can "like" 0-many Posts, so I set it up exactly as stated above.  My issue now is that for a given Post or set of Posts, I need to query how many users have liked each Post.  I'm having trouble figuring out how to query for that... Can someone help me out? I'm not sure if this is a limitation or if I just don't know enough to figure this out.  I've thought about storing a counter on the Post itself and using increment() and decrement() each time a User likes or unlikes a Post, but I'd rather not if I can get away with it.</p>