title: Mongo query returns null even though entry is returned by find
body: <p>In our MongoDb we are implementing the following document structure:</p>
  
  <pre><code>Parent
     |-- List&lt;Children&gt;
                  |-- ChildField1
                  |-- ChildField2
                  ...
  </code></pre>
  
  <p>So we have a top level document that contains a list of child documents where each has some members. One of our queries performs a findOne on the value of ChildField1 which is a string. This works as long as the size of the string is not too long. As soon as we store larger strings (in my test it was larger than 1011 chars) we can store the document but the findOne always returns "null". </p>
  
  <p>This happens the same no matter if I use Spring Mongo Data or fire the query in the mongo shell so I figure this is a Mongo issue. When I call find() on the collection all elements are shown but as soon as add a query for the value nothing is returned even by find.</p>
  
  <p>Can anyone tell me what the problem is here and how I can fix it?</p>