public function getCol($query, $parameters = [])
    {
        // @deprecated since v6.0 (2016-04-13); Backward compatibility for v5.3.0.
        $parameters = $this->assureParameterIsAnArray($parameters);
        // END deprecated

        $result = [];

        try {
            $rows = $this->getConnection()->fetchAll($query, $parameters);
            foreach ($rows as $row) {
                // cause there is no doctrine equivalent, we take this little detour and restructure the result
                $columnNames = array_keys($row);
                $columnName = $columnNames[0];

                $result[] = $row[$columnName];
            }
        } catch (DBALException $exception) {
            $exception = $this->convertException($exception);
            $this->handleException($exception);
        } catch (PDOException $exception) {
            $exception = $this->convertException($exception);
            $this->handleException($exception);
        }

        return $result;
    }