Doctrine\DBAL\Connection::rollBack PHP Method

    public function rollBack()
    {
        if ($this->_transactionNestingLevel == 0) {
            throw ConnectionException::noActiveTransaction();
        }
        $this->connect();
        $logger = $this->_config->getSQLLogger();
        if ($this->_transactionNestingLevel == 1) {
            if ($logger) {
                $logger->startQuery('"ROLLBACK"');
            }
            $this->_transactionNestingLevel = 0;
            $this->_conn->rollBack();
            $this->_isRollbackOnly = false;
            if ($logger) {
                $logger->stopQuery();
            }
            if (false === $this->autoCommit) {
                $this->beginTransaction();
            }
        } elseif ($this->_nestTransactionsWithSavepoints) {
            if ($logger) {
                $logger->startQuery('"ROLLBACK TO SAVEPOINT"');
            }
            $this->rollbackSavepoint($this->_getNestedTransactionSavePointName());
            --$this->_transactionNestingLevel;
            if ($logger) {
                $logger->stopQuery();
            }
        } else {
            $this->_isRollbackOnly = true;
            --$this->_transactionNestingLevel;
        }
    }

 public function exportData($export, $reporter)
 {
     $this->conn->beginTransaction();
     try {
         $lastExportedAt = (int) $export['lastExportedAt'];
         $areas = $this->conn->fetchAll('SELECT a.`id`, a.`name`, t.`id` AS `territoryId`, t.`name` AS `territoryName`, a.`customData`, a.`lastUpdatedAt` ' . 'FROM `' . CoreTables::AREA_TBL . '` a ' . 'INNER JOIN `' . CoreTables::TERRITORY_TBL . '` t ON t.`id` = a.`territoryId` ' . 'WHERE a.`projectId` = :projectId AND a.`statusId` = :statusId', [':projectId' => $export['projectId'], ':statusId' => $export['areaStatusId']]);
         $block = new ExportBlock();
         foreach ($areas as $area) {
             $block->addId($area['id']);
             if ($area['lastUpdatedAt'] > $lastExportedAt) {
                 $area['customData'] = json_decode($area['customData']);
                 $block->addUpdatedId($area['id']);
                 $block->addUpdate($area);
             }
         }
         $event = new ExportEvent($export['projectId'], $export['lastExportedAt'], $reporter);
         $event->addBlock('area', $block);
         $event = $this->eventDispatcher->dispatch(ExportEvents::EXPORT_ONGOING, $event);
         $this->conn->executeQuery('UPDATE `' . ExportTables::DATA_EXPORT_TBL . '` SET `lastExportedAt` = :time WHERE `id` = :id', [':time' => time(), ':id' => $export['id']]);
         $this->conn->commit();
         return $event->output();
     } catch (Exception $ex) {
         $this->conn->rollBack();
         throw $ex;
     }
 }