bug 5716 ..about Compatibility with DB2?

Hello.

I'm trying to enable using expression in order clause.
In the task , I found next code with some comment.

//bug 5716 - for db2 compatibility - no qualified names allowed in order by 
clause when union/union all operator is used

 if (target instanceof SetOperatorNode && correlationName != null)
 {
  String fullName = (schemaName != null) ?
   (schemaName + "." + correlationName + "." + columnName) :
   (correlationName + "." + columnName);
  throw 
StandardException.newException(SQLState.LANG_QUALIFIED_COLUMN_NAME_NOT_ALLOWED, 
fullName);
 }

Does anyone know anything about this ?
If possible, I want to ommit this code.....

Best regards.

/*

        Tomohito Nakayama
        tomoihto-3vbGXx/L6hogx5LJoh7VlA@xxxxxxxxxxxxxxxx
        tomonaka-w3tBFbkRwq9dvEbG9P4ZtA@xxxxxxxxxxxxxxxx

        Naka
        http://www5.ocn.ne.jp/~tomohito/TopPage.html

*/ 



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