title: How to get duplicate field values in elastic search by field name without knowing its value
body: <p>I have a field "EmployeeName" in an elastic search index - and I would like to execute a query that will return me all the cases where there are duplicate values of "EmployeeName". Can this be done?</p>
  
  <p>I found more_like_this but this requires field value for "like_text".
  But my requirement is to get  list of employees who are having duplicate names without knowing its value.</p>
  
  <pre><code>{
      "more_like_this" : {
          "fields" : ["EmployeeName"],
          "like_text" : "Mukesh",
          "min_term_freq" : 1,
          "max_query_terms" : 12
      }
  }
  </code></pre>
  
  <p>Thanks in Advance</p>
  
  <p>Regards
  Mukesh</p>