Hi, for type strategies you can check out org.apache.flink.table.types.inference.InputTypeStrategies. They are pretty extensive and widely covers most use cases. In your case, this function probably requires the COMMON type strategy. If you want to roll out your own type inference, look at the org.apache.flink.table.types.inference.strategies package, you can find all the type strategies we have inside it.
On Mon, Sep 20, 2021 at 4:39 PM Seth Wiesman <sjwies...@gmail.com> wrote: > The type strategy can be generic over the input and output types, so you > can write something generic that say given a multiset of some type T this > function returns an array of some type T. This is the exact same logic > built-in functions use and is just as expressive as anything Flink could > provide. > > Seth > > On Mon, Sep 20, 2021 at 1:26 AM Kai Fu <zzfu...@gmail.com> wrote: > >> Hi Seth, >> >> This is really helpful and inspiring, thank you for the information. >> >> On Sun, Sep 19, 2021 at 11:06 PM Seth Wiesman <sjwies...@gmail.com> >> wrote: >> >>> Hi, >>> >>> I agree it would be great to see these functions built-in, but you do >>> not need to write a UDF for each type. You can overload a UDFs type >>> inference and have the same capabilities as built-in functions, which means >>> supporting generics. >>> >>> >>> https://github.com/apache/flink/blob/master/flink-examples/flink-examples-table/src/main/java/org/apache/flink/table/examples/java/functions/LastDatedValueFunction.java >>> >>> On Sat, Sep 18, 2021 at 7:42 AM Yuval Itzchakov <yuva...@gmail.com> >>> wrote: >>> >>>> Hi Jing, >>>> >>>> I recall there is already an open ticket for built-in aggregate >>>> functions >>>> >>>> On Sat, Sep 18, 2021, 15:08 JING ZHANG <beyond1...@gmail.com> wrote: >>>> >>>>> Hi Yuval, >>>>> You could open a JIRA to track this if you think some functions should >>>>> be added as built-in functions in Flink. >>>>> >>>>> Best, >>>>> JING ZHANG >>>>> >>>>> Yuval Itzchakov <yuva...@gmail.com> 于2021年9月18日周六 下午3:33写道： >>>>> >>>>>> The problem with defining a UDF is that you have to create one >>>>>> overload per key type in the MULTISET. It would be very convenient to >>>>>> have >>>>>> functions like Snowflakes ARRAY_AGG. >>>>>> >>>>>> On Sat, Sep 18, 2021, 05:43 JING ZHANG <beyond1...@gmail.com> wrote: >>>>>> >>>>>>> Hi Kai, >>>>>>> AFAIK, there is no built-in function to extract the keys in MULTISET >>>>>>> <https://ci.apache.org/projects/flink/flink-docs-release-1.13/docs/dev/table/types/> >>>>>>> to >>>>>>> be an ARRAY. Define a UTF is a good solution. >>>>>>> >>>>>>> Best, >>>>>>> JING ZHANG >>>>>>> >>>>>>> Kai Fu <zzfu...@gmail.com> 于2021年9月18日周六 上午7:35写道： >>>>>>> >>>>>>>> Hi team, >>>>>>>> >>>>>>>> We want to know if there is any built-in function to extract the >>>>>>>> keys in MULTISET >>>>>>>> <https://ci.apache.org/projects/flink/flink-docs-release-1.13/docs/dev/table/types/> >>>>>>>> to be an ARRAY. There is no such function as far as we can find, >>>>>>>> except to >>>>>>>> define a simple wrapper UDF for that, please advise. >>>>>>>> >>>>>>>> -- >>>>>>>> *Best wishes,* >>>>>>>> *- Kai* >>>>>>>> >>>>>>> >> >> -- >> *Best wishes,* >> *- Kai* >> >
