presto-main/src/main/java/io/prestosql/execution/QueryIdGenerator.java/QueryIdGenerator/QueryIdGenerator
class QueryIdGenerator:    public QueryIdGenerator()
    {
        StringBuilder coordinatorId = new StringBuilder(5);
        for (int i = 0; i < 5; i++) {
            coordinatorId.append(BASE_32[ThreadLocalRandom.current().nextInt(32)]);
        }
        this.coordinatorId = coordinatorId.toString();
    }