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 >>> >>
