if (keyNames == null || keyNames.length == 0) { return EMPTY_COLUMNS; }
    protected static Column[] getPrimaryKeys(Column[] columns, String[] keyNames)    {        List keyList = new ArrayList();        for (int i = 0; i < keyNames.length; i++)        {            Column primaryKey = DataSetUtils.getColumn(keyNames[i], columns);            if (primaryKey != null)            {                keyList.add(primaryKey);            }//            else//            {//                // primary key not found in table//                if (_primaryKeys[i] == null)//                {//                    throw new NoPrimaryKeyException("<" + primaryKeys[i] +//                            "> not found in table <" + tableName + ">");//                }//            }        }        return (Column[])keyList.toArray(new Column[0]);    }