bundle/Installer/BaseInstaller.php
protected function importDataFile(string $dataFile, string $controlTableName = null): void
    {
        if ($controlTableName !== null) {
            $query = $this->db->createQueryBuilder();
            $query->select('count(*) AS count')
                ->from($controlTableName);

            $data = $query->execute()->fetchAll();

            $contentCount = (int) $data[0]['count'];
            if ($contentCount > 0) {
                $this->output->writeln('<comment>Data already exists in the database, skipping data import for file <info>' . $dataFile . '</info></comment>');

                return;
            }
        }

        $this->runQueriesFromFile($dataFile);
    }
protected function importDataFile(string $dataFile, string $controlTableName = null): void
    {
        if ($controlTableName !== null) {
            $query = $this->db->createQueryBuilder();
            $query->select('count(*) AS count')
                ->from($controlTableName);

            $data = $query->execute()->fetchAll();

            $contentCount = (int) $data[0]['count'];
            if ($contentCount > 0) {
                $this->output->writeln('<comment>Data already exists in the database, skipping data import for file <info>' . $dataFile . '</info></comment>');

                return;
            }
        }

        $this->runQueriesFromFile($dataFile);
    }
Handle inserting of sql dump, sql dump should ideally be in ISO SQL format.

Data file is created with: mysqldump ngsite --no-create-info --extended-insert=false > data.sql