Hi, Jingsong. It's hard to provide an option regarding to the fact that we also want to decouple Hive with flink planner. If we still need this fall back behavior, we will still depend on `ParserImpl` provided by flink-table-planner on HiveParser. But to try best to minimize the impact to users and more user-friendly, I'll remind users may use set table.sql-dialect = default to switch to Flink's default dialect in error message when fail to parse the sql in HiveParser.
Best regards, Yuxia Best regards, Yuxia ----- 原始邮件 ----- 发件人: "Jingsong Li" <jingsongl...@gmail.com> 收件人: "Rui Li" <lirui.fu...@gmail.com> 抄送: "dev" <dev@flink.apache.org>, "yuxia" <luoyu...@alumni.sjtu.edu.cn>, "User" <u...@flink.apache.org> 发送时间: 星期二, 2023年 5 月 30日 下午 3:21:56 主题: Re: [DISCUSS] Hive dialect shouldn't fall back to Flink's default dialect +1, the fallback looks weird now, it is outdated. But, it is good to provide an option. I don't know if there are some users who depend on this fallback. Best, Jingsong On Tue, May 30, 2023 at 1:47 PM Rui Li <lirui.fu...@gmail.com> wrote: > > +1, the fallback was just intended as a temporary workaround to run > catalog/module related statements with hive dialect. > > On Mon, May 29, 2023 at 3:59 PM Benchao Li <libenc...@apache.org> wrote: >> >> Big +1 on this, thanks yuxia for driving this! >> >> yuxia <luoyu...@alumni.sjtu.edu.cn> 于2023年5月29日周一 14:55写道： >> >> > Hi, community. >> > >> > I want to start the discussion about Hive dialect shouldn't fall back to >> > Flink's default dialect. >> > >> > Currently, when the HiveParser fail to parse the sql in Hive dialect, >> > it'll fall back to Flink's default parser[1] to handle flink-specific >> > statements like "CREATE CATALOG xx with (xx);". >> > >> > As I‘m involving with Hive dialect and have some communication with >> > community users who use Hive dialectrecently, I'm thinking throw exception >> > directly instead of falling back to Flink's default dialect when fail to >> > parse the sql in Hive dialect >> > >> > Here're some reasons: >> > >> > First of all, it'll hide some error with Hive dialect. For example, we >> > found we can't use Hive dialect any more with Flink sql client in release >> > validation phase[2], finally we find a modification in Flink sql client >> > cause it, but our test case can't find it earlier for although HiveParser >> > faill to parse it but then it'll fall back to default parser and pass test >> > case successfully. >> > >> > Second, conceptually, Hive dialect should be do nothing with Flink's >> > default dialect. They are two totally different dialect. If we do need a >> > dialect mixing Hive dialect and default dialect , may be we need to propose >> > a new hybrid dialect and announce the hybrid behavior to users. >> > Also, It made some users confused for the fallback behavior. The fact >> > comes from I had been ask by community users. Throw an excpetioin directly >> > when fail to parse the sql statement in Hive dialect will be more >> > intuitive. >> > >> > Last but not least, it's import to decouple Hive with Flink planner[3] >> > before we can externalize Hive connector[4]. If we still fall back to Flink >> > default dialct, then we will need depend on `ParserImpl` in Flink planner, >> > which will block us removing the provided dependency of Hive dialect as >> > well as externalizing Hive connector. >> > >> > Although we hadn't announced the fall back behavior ever, but some users >> > may implicitly depend on this behavior in theirs sql jobs. So, I hereby >> > open the dicussion about abandoning the fall back behavior to make Hive >> > dialect clear and isoloted. >> > Please remember it won't break the Hive synatax but the syntax specified >> > to Flink may fail after then. But for the failed sql, you can use `SET >> > table.sql-dialect=default;` to switch to Flink dialect. >> > If there's some flink-specific statements we found should be included in >> > Hive dialect to be easy to use, I think we can still add them as specific >> > cases to Hive dialect. >> > >> > Look forwards to your feedback. I'd love to listen the feedback from >> > community to take the next steps. >> > >> > [1]: >> > https://github.com/apache/flink/blob/678370b18e1b6c4a23e5ce08f8efd05675a0cc17/flink-connectors/flink-connector-hive/src/main/java/org/apache/flink/table/planner/delegation/hive/HiveParser.java#L348 >> > [2]:https://issues.apache.org/jira/browse/FLINK-26681 >> > [3]:https://issues.apache.org/jira/browse/FLINK-31413 >> > [4]:https://issues.apache.org/jira/browse/FLINK-30064 >> > >> > >> > >> > Best regards, >> > Yuxia >> > >> >> >> -- >> >> Best, >> Benchao Li > > > > -- > Best regards! > Rui Li
