presto-main/src/main/java/io/prestosql/execution/QueryIdGenerator.java/QueryIdGenerator/createNextQueryId
class QueryIdGenerator:    public synchronized QueryId createNextQueryId()
    {
        // only generate 100,000 ids per day
        if (counter > 99_999) {
            // wait for the second to rollover
            while (MILLISECONDS.toSeconds(nowInMillis()) == lastTimeInSeconds) {
                Uninterruptibles.sleepUninterruptibly(1, TimeUnit.SECONDS);
            }
            counter = 0;
        }

        // if it has been a second since the last id was generated, generate a new timestamp
        long now = nowInMillis();
        if (MILLISECONDS.toSeconds(now) != lastTimeInSeconds) {
            // generate new timestamp
            lastTimeInSeconds = MILLISECONDS.toSeconds(now);
            lastTimestamp = TIMESTAMP_FORMAT.print(now);

            // if the day has rolled over, restart the counter
            if (MILLISECONDS.toDays(now) != lastTimeInDays) {
                lastTimeInDays = MILLISECONDS.toDays(now);
                counter = 0;
            }
        }

        return new QueryId(format("%s_%05d_%s", lastTimestamp, counter++, coordinatorId));
    }