title: MarkLogic: using cts:search to find elements without text
body: <p>I want to find all documents that don't have any text within a certain element - this works but is very slow:</p>
  
  <pre><code>let $not-empty := for $i in cts:search(//foo[@class="bar"][text()[not(. = '')]] ,
                                    cts:and-query(())
                                      ) 
                                   return base-uri($i)
  </code></pre>
  
  <p>how can I use the indexes effectively to search for elements without a text node and where the text node doesn't contain any characters?</p>