title: Will MySQL Optimize the lower half of a union query
body: <p>Is there any way (or is it automatic) for MySQL to optimize the bottom half of a UNION ALL query if I impose a LIMIT statement on the number of results which should be returned. For instance if I have a query as such:</p>
  
  <pre><code>SELECT ID FROM MyTable WHERE Match (NameColumn) Against ('seachterm')
  UNION ALL
  SELECT ID FROM MyTable WHERE (DescriptionColumn) Against ('seachterm')
  LIMIT 10;
  </code></pre>
  
  <p>If I run this query and the first query for an match in the name returns 15 results, there should be no reason to even run the second query, as I already have enough results. Does MySQL Optimize away the second query, or is there a way to tell it to do so?  Based on performing the query with EXPLAIN EXTENDED in front, it doesn't appear as though the second part is optimized away.</p>