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* >
