presto-redis/src/main/java/io/prestosql/plugin/redis/RedisRecordCursor.java/RedisRecordCursor/fetchKeys
class RedisRecordCursor:    private boolean fetchKeys()
    {
        try (Jedis jedis = jedisPool.getResource()) {
            switch (split.getKeyDataType()) {
                case STRING: {
                    String cursor = SCAN_POINTER_START;
                    if (redisCursor != null) {
                        cursor = redisCursor.getStringCursor();
                    }

                    log.debug("Scanning new Redis keys from cursor %s . %d values read so far", cursor, totalValues);

                    redisCursor = jedis.scan(cursor, scanParms);
                    List<String> keys = redisCursor.getResult();
                    keysIterator = keys.iterator();
                }
                break;
                case ZSET:
                    Set<String> keys = jedis.zrange(split.getKeyName(), split.getStart(), split.getEnd());
                    keysIterator = keys.iterator();
                    break;
                default:
                    log.debug("Redis type of key %s is unsupported", split.getKeyDataFormat());
                    return false;
            }
        }
        return true;
    }