presto-spi/src/main/java/io/prestosql/spi/type/CharType.java/CharType/compareTo
class CharType:    @Override
    public int compareTo(Block leftBlock, int leftPosition, Block rightBlock, int rightPosition)
    {
        Slice leftSlice = leftBlock.getSlice(leftPosition, 0, leftBlock.getSliceLength(leftPosition));
        Slice rightSlice = rightBlock.getSlice(rightPosition, 0, rightBlock.getSliceLength(rightPosition));

        return compareChars(leftSlice, rightSlice);
    }