title: JPQL 'Function' doesn't send operator
body: <p>I am using <code>EclipseLink</code> over <code>Spring Boot</code> and have this jpql in a repository:</p>
  <pre><code>    @Query(&quot;select function('pMonth',p.payDay) ,sum(p.price) &quot; +
              &quot;from FullPayment p where &quot; +
              &quot;group by function('pMonth', p.payDay)&quot;
      )
      List&lt;Object[]&gt; paymentMonthlyHistory();
  </code></pre>
  <p>but it does not send the operator <code>p.payDay</code> calling my custom function <code>pMonth</code>. Here is the database error:</p>
  <pre><code>Internal Exception: com.mysql.jdbc.exceptions.jdbc4.MySQLSyntaxErrorException: Incorrect number of arguments for FUNCTION adventure_db.pMonth; expected 1, got 0
  Error Code: 1318
  Call: SELECT pMonth(), SUM(PRICE) FROM panel_fullPayment WHERE ((PAYDATE &gt;= ?) AND (TRANSACTIONAMOUNT &gt;= PRICE)) GROUP BY pMonth()
      bind =&gt; [1 parameter bound]
  </code></pre>
  <p>I use <code>Mysql</code> as DBMS. Any help would be appreciated</p>