public static boolean isOpCast(ExprNodeDesc desc) {
    if (!(desc instanceof ExprNodeGenericFuncDesc)) {
      return false;
    }
    return isOpCast(((ExprNodeGenericFuncDesc)desc).getGenericUDF());
  }
Returns whether the exprNodeDesc is node of "cast".
ql/src/java/org/apache/hadoop/hive/ql/exec/FunctionRegistry.java