@Override
  public int hashCode() {
    int superHashCode = super.hashCode();
    HashCodeBuilder builder = new HashCodeBuilder();
    builder.appendSuper(superHashCode);
    builder.append(children);
    return builder.toHashCode();
  }
Create a ExprNodeGenericFuncDesc based on the genericUDFClass and the
children parameters. If the function has an explicit name, the
newInstance method should be passed the function name in the funcText
argument.

@throws UDFArgumentException
ql/src/java/org/apache/hadoop/hive/ql/plan/ExprNodeGenericFuncDesc.java