Hi Wangsan,
If your require is essentially wha Jark describe, we already have a
proposal following up [FLINK-9249] in its related/parent task:
[FLINK-9484]. We are already implementing some of these internally and have
one PR ready for review for FLINK-9294.
Please kindly take a look and see if there's any additional features you
would like to comment and suggest.
Thanks,
Rong
On Fri, Nov 30, 2018 at 1:54 AM Jark Wu <imj...@gmail.com> wrote:
> Hi Wangsan,
>
> If I understand correctly, you want the return type of UDTF is determined
> by the actual arguments, not a fixed result type. For example:
>
> udtf("int, string, long", inputField) returns a composite type with
> [f0: INT, f1: VARCHAR, f2: BIGINT]
> udtf("int", inputField) returns an atomic type with [f0: INT]
>
> This is an interesting and useful feature IMO. But it maybe need some
> modification for the current API of TableFunction to
> provide an additional `TypeInformation[T] getResultType(Object[]
> arguments, Class[] argTypes)` interface. Which means need
> more discussion in the community.
>
> But you can create an issue if this is what you want and we can discuss
> how to support it.
>
> Best,
> Jark
>
>
>
> On Thu, 29 Nov 2018 at 19:14, Timo Walther <twal...@apache.org> wrote:
>
>> Hi Wangsan,
>>
>> currently, UDFs have very strict result type assumptions. This is
>> necessary to determine the serializers for the cluster. There were
>> multiple requests for more flexible handling of types in UDFs.
>>
>> Please have a look at:
>> - [FLINK-7358] Add implicitly converts support for User-defined function
>> - [FLINK-9294] [table] Improve type inference for UDFs with composite
>> parameter and/or result type
>> - [FLINK-10958] [table] Add overload support for user defined function
>>
>> I you think those issues do not represent what you need. You can open a
>> new issue with a little example of what feature you think is missing.
>>
>> Regards,
>> Timo
>>
>>
>> Am 28.11.18 um 09:59 schrieb wangsan:
>> > Hi all,
>> >
>> > When using user-defined table function in Flink SQL, it seems that the
>> result type of a table function must be determinstic.
>> >
>> > If I want a UDTF whose result type is determined by its input
>> parameters, what should I do?
>> >
>> > What I want to do is like this:
>> >
>> > ```
>> > SELECT input, f1, f2 length FROM MyTable, LATERAL
>> TABLE(unnest_udtf(input, v1, v2)) as T(f1, f2), LATERAL
>> TABLE(unnest_udtf(input, v3, v4, v5)) as T(f3, f4, f5)
>> > ```
>> >
>> > I can surely register the same UDTF with different name and
>> configuration, but I guess that’s not a good idea :(.
>> >
>> > If we can not make this in Flink SQL for now , may be we should
>> consider this feature in future?
>> >
>> > Best,
>> > wangsan
>>
>>
>>
