presto-jdbc/src/main/java/io/prestosql/jdbc/QueryStats.java/QueryStats/getProgressPercentage
class QueryStats:    public OptionalDouble getProgressPercentage()
    {
        if (!scheduled || totalSplits == 0) {
            return OptionalDouble.empty();
        }
        return OptionalDouble.of(min(100, (completedSplits * 100.0) / totalSplits));
    }