presto-hive/src/main/java/io/prestosql/plugin/hive/util/Statistics.java/Statistics/mergeBooleanStatistics
class Statistics:    private static Optional<BooleanStatistics> mergeBooleanStatistics(Optional<BooleanStatistics> first, Optional<BooleanStatistics> second)
    {
        // normally, either both or none is present
        if (first.isPresent() && second.isPresent()) {
            return Optional.of(new BooleanStatistics(
                    reduce(first.get().getTrueCount(), second.get().getTrueCount(), ADD, false),
                    reduce(first.get().getFalseCount(), second.get().getFalseCount(), ADD, false)));
        }
        return Optional.empty();
    }