title: Lucene not null query?
body: <p>How can we construct a query to search for particular field to be not null?</p>
  
  <p><code>field_name:*</code> is not working.
  I tried <code>field_name:[a* to z*]</code> this works fine for English, but does not cover all languages.</p>
  
  <p>Any alternative suggestions?</p>