public function loadAll(array $columnNames = null)
    {
        if (is_array($columnNames)) {
            foreach ($columnNames as $columnName) {
                $this->columnsToLoad[$columnName] = $this->structure->getColumn($columnName);
            }
        } else {
            $this->columnsToLoad = $this->structure->getColumns();
        }

        return $this;
    }