presto-main/src/main/java/io/prestosql/type/VarcharOperators.java/VarcharOperators/notEqual
class VarcharOperators:    @LiteralParameters("x")
    @ScalarOperator(NOT_EQUAL)
    @SqlType(StandardTypes.BOOLEAN)
    @SqlNullable
    public static Boolean notEqual(@SqlType("varchar(x)") Slice left, @SqlType("varchar(x)") Slice right)
    {
        return !left.equals(right);
    }