title: Arel Query CAST operation
body: <p>I need to form a query in Arel which had a CAST operation earlier. The original query was like : 
      select * from tablename where tablename.anniversary >= CAST(STR_TO_DATE(?,'%d-%m-%Y-%k-%i-%s') as DATETIME)</p>
  
  <p>(the question mark is replaced by actual date in further code)</p>
  
  <p>For the where condition, I am doing this :</p>
  
  <pre><code>where(tablename['anniversary']
                         .gteq("CAST(STR_TO_DATE(#{date_value},'%d-%m-%Y %k:%i') as DATETIME)"))
  </code></pre>
  
  <p>The final resulting query that I should get should have :
      tablename.anniversary >= '2015-07-13 16:12:00'</p>
  
  <p>But I get :</p>
  
  <pre><code>tablename.anniversary &gt;= 'CAST(STR_TO_DATE(13-09-2015 05:33PM,\'%d-%m-%Y %k:%i\') as DATETIME)'
  </code></pre>
  
  <p>What am I doing wrong ?</p>