presto-accumulo/src/main/java/io/prestosql/plugin/accumulo/iterators/MinByteArrayCombiner.java/MinByteArrayCombiner/reduce
class MinByteArrayCombiner:    @Override
    public Value reduce(Key key, Iterator<Value> iter)
    {
        Value min = null;
        while (iter.hasNext()) {
            Value test = iter.next();
            if (min == null) {
                min = new Value(test.get());
            }
            else if (comparator.compare(test.get(), min.get()) < 0) {
                min.set(test.get());
            }
        }
        return min;
    }