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
