presto-main/src/main/java/io/prestosql/type/CharOperators.java/CharDistinctFromOperator/isDistinctFrom
class CharDistinctFromOperator:        @LiteralParameters("x")
        @SqlType(StandardTypes.BOOLEAN)
        public static boolean isDistinctFrom(
                @BlockPosition @SqlType(value = "char(x)", nativeContainerType = Slice.class) Block left,
                @BlockIndex int leftPosition,
                @BlockPosition @SqlType(value = "char(x)", nativeContainerType = Slice.class) Block right,
                @BlockIndex int rightPosition)
        {
            if (left.isNull(leftPosition) != right.isNull(rightPosition)) {
                return true;
            }
            if (left.isNull(leftPosition)) {
                return false;
            }

            int leftLength = left.getSliceLength(leftPosition);
            int rightLength = right.getSliceLength(rightPosition);
            if (leftLength != rightLength) {
                return true;
            }
            return !left.equals(leftPosition, 0, right, rightPosition, 0, leftLength);
        }