pool = None
    for item in db.file.find({}, limit=100000, no_cursor_timeout=True):
        count += 1
        stat.tick()
        if pool is None or not count % 10000:
            pool = ProcessPoolExecutor(max_workers=1)
            print('Pool reseted')
        try:
            fut = pool.submit(process_file, item['path'], item['_id'])
        except Exception as ex: 
            error_logger('URL: %s, error: %s' % (item['url'], item['_id']))
        else:
            comp = fut.result()
            extra_fields = extra_fields.union([x[0] for x in comp['extra_fields']])