code: private function entryExists($hash)
      {
          $queryBuilder = $this->connection->createQueryBuilder();
          $queryBuilder->from($this->table, 'backlog');
          $queryBuilder->andWhere('backlog.hash = :hash');
          $queryBuilder->setParameter(':hash', $hash);
          $queryBuilder->setMaxResults(1);
          $queryBuilder->select('backlog.id');
  
          $backlog = $queryBuilder->execute()->fetch(PDO::FETCH_ASSOC);
  
          if (!empty($backlog)) {
              return true;
          }
  
          return false;
      }
docs: @param string $hash
  
  @return bool