Hello everyone I'd like to revive FLIP-154[1] a bit.
I failed with finding any discussion/vote thread about it (please point me to that if it is present somewhere) Also FLIP itself looks abandoned (no activity for a couple of years), however it seems to be useful. I did a bit investigation about that >From one side Calcite provides its own coercion... However, sometimes it behaves strangely and is not ready to use in Flink. for instance 1) it can not handle cases with `with` subqueries and fails with NPE (even if it's fixed it will come not earlier than with 1.36.0) 2) under the hood it uses hardcoded `cast`, especially it is an issue for equals where `cast` is invoked without fallback to `null`. In addition it tries to cast `string` to `date`. All this leads to failure for such queries like `select uuid() = null;` where it tries to cast the result of `uuid()` to date without a fallback option. The good thing is that Calcite also provides a custom TypeCoercionFactory which could be used during coercion (in case it is enabled). This could allow for instance to use `try_cast` instead of `cast`, embed the fix for aforementioned NPE, enable only required coercion rules. Also it will enable coercions rule by rule instead of big bang. I would volunteer to update the FLIP page with usage of a custom factory if there are no objections and come back with a discussion thread to revive the work on it. [1] https://cwiki.apache.org/confluence/display/FLINK/FLIP-154%3A+SQL+Implicit+Type+Coercion -- Best regards, Sergey
