protected function _isDirty($column = null)
{
if ($column) {
$mapping = $this->_model->getUnionColumnMapping();
$columns = get_class_vars($mapping);
$columns = $columns['columns'];
if (in_array($column, $columns)) {
return $this->_sourceRow->isDirty($column);
} else {
return parent::_isDirty($column);
}
} else {
return parent::_isDirty() || $this->_sourceRow->isDirty();
}
}
