title: Reactive updates when query is filtered by another query
body: <p>I just started using meteor today and can't seem to figure out what I'm doing wrong. I have a query that is being run inside of a publish function, but this query is filtered by the result of another query.</p>
  
  <p>In short, when I add a document to the database that is being published (CollectionTwo) it works as I would expect, but when I make my change in the database that is being used to filter (CollectionOne), meteor doesn't behave reactively.</p>
  
  <pre><code>CollectionOne = new Meteor.Collection("one")
  CollectionTwo = new Meteor.Collection("two")
  
  Meteor.publish("items", -&gt;
    not_hidden = CollectionOne.find().fetch()
    return CollectionTwo.find( _id: {'$in':( t.my_id for t in not_hidden )} )
  )
  </code></pre>
  
  <p>Meanwhile, on the client...</p>
  
  <pre><code>CollectionOne = new Meteor.Collection("one")
  CollectionTwo = new Meteor.Collection("two")
  
  Meteor.subscribe("items")
  
  _.extend( Template.items,
    items: -&gt;
      not_hidden = CollectionOne.find().fetch()
      return CollectionTwo.find( _id: {'$in':( t.my_id for t in not_hidden )} )
  )
  </code></pre>
  
  <p>Any ideas what the appropriate solution might be?</p>