Hi, Jark
FYI, this feature has already been supported in Calcite 1.33.0 [1].
Therefore, I believe we can use it directly after upgrading the Calcite
version.
Best,
Aitozi.
[1]: https://issues.apache.org/jira/browse/CALCITE-5305
Aitozi <gjying1...@gmail.com> 于2023年3月6日周一 16:48写道：
> Thanks, will give it a try
>
> Best,
> Aitozi.
>
> Jark Wu <imj...@gmail.com> 于2023年3月6日周一 15:11写道：
>
>> Hi Aitozi,
>>
>> I would suggest trying to contribute it to the upstream project Calcite
>> first.
>>
>> Best,
>> Jark
>>
>> > 2023年3月6日 11:51，Aitozi <gjying1...@gmail.com> 写道：
>> >
>> > Hi Jark,
>> >
>> > Thank you for your helpful suggestion. It appears that 'E'foo\n'' is a
>> more
>> > versatile and widely accepted option. To assess its feasibility, I have
>> > reviewed the relevant Unicode supports and concluded that it may
>> > necessitate modifications to the Parser.jj file to accommodate this new
>> > syntax.
>> >
>> >
>> > I am unsure whether we should initially incorporate this alteration in
>> > Calcite or if we can directly supersede the StringLiteral behavior
>> within
>> > the Flink project. Nevertheless, I believe supporting this change is
>> > achievable.
>> >
>> >
>> >
>> > Thanks,
>> > Aitozi.
>> >
>> > Jark Wu <imj...@gmail.com> 于2023年3月6日周一 10:16写道：
>> >
>> >> Hi Aitozi,
>> >>
>> >> I think this is a good idea to improve the backslash escape strings.
>> >> However, I lean a bit more toward the Postgres approach[1],
>> >> which is more standard-compliant. PG allows backslash escape
>> >> string by writing the letter E (upper or lower case) just before the
>> >> opening single quote, e.g., E'foo\n'.
>> >>
>> >> Recognizing backslash escapes in both regular and escape string
>> constants
>> >> is not backward compatible in Flink, and is also deprecated in PG.
>> >>
>> >> In addition, Flink also supports Unicode escape string constants by
>> >> writing the U& before the quote[1] which works in the same way with
>> >> backslash escape string.
>> >>
>> >> Best,
>> >> Jark
>> >>
>> >> [1]:
>> >>
>> >>
>> https://www.postgresql.org/docs/current/sql-syntax-lexical.html#SQL-SYNTAX-CONSTANTS
>> >> [2]:
>> >>
>> >>
>> https://nightlies.apache.org/flink/flink-docs-master/docs/dev/table/sql/queries/overview/
>> >>
>> >> On Sat, 4 Mar 2023 at 23:31, Aitozi <gjying1...@gmail.com> wrote:
>> >>
>> >>> Hi,
>> >>> I encountered a problem when using string literal in Flink.
>> Currently,
>> >>> Flink will escape the string literal during codegen, so for the query
>> >>> below:
>> >>>
>> >>> SELECT 'a\nb'; it will print => a\nb
>> >>>
>> >>> then for the query
>> >>>
>> >>> SELECT SPLIT_INDEX(col, '\n', 0);
>> >>>
>> >>> The col can not split by the newline. If we want to split by the
>> newline,
>> >>> we should use
>> >>>
>> >>> SELECT SPLIT_INDEX(col, '
>> >>> ', 0)
>> >>>
>> >>> or
>> >>>
>> >>> SELECT SPLIT_INDEX(col, CHR(10), 0)
>> >>>
>> >>> The above way could be more intuitive. Some other databases support
>> these
>> >>> "Special Character Escape Sequences"[1].
>> >>>
>> >>> In this way, we can directly use
>> >>> SELECT SPLIT_INDEX(col, '\n', 0); for the query.
>> >>>
>> >>> I know this is not standard behavior in ANSI SQL. I'm opening this
>> thread
>> >>> for some opinions from the community guys.
>> >>>
>> >>> [1]:
>> >>>
>> >>>
>> >>
>> https://dev.mysql.com/doc/refman/8.0/en/string-literals.html#character-escape-sequences
>> >>>
>> >>> Thanks,
>> >>> Aitozi
>> >>>
>> >>
>>
>>
