title: DQL: enable (return_top 10) performance impact
body: <p>I had this query that originally caused massive timeouts:</p>
  
  <pre><code>select d.r_object_id 
  from isc_fiche  d, dmr_con c 
  where any c.parent_id = d.r_object_id 
  group by d.r_object_id 
  having count(*) &gt; 2 
  </code></pre>
  
  <p>yet when I add the <code>enable (return_top 10)</code> to the end then the performance issues seem a thing off the past. Apparently (according to colleagues) that statement could have a perfomance-improving effect.</p>
  
  <p>Could someone clarify this for me?</p>
  
  <p>Full query with 'way' better performance:</p>
  
  <pre><code>select d.r_object_id 
  from isc_fiche  d, dmr_con c 
  where any c.parent_id = d.r_object_id 
  group by d.r_object_id 
  having count(*) &gt; 2 
  enable(return_top 10)
  </code></pre>