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From Till Rohrmann <trohrm...@apache.org>
Subject Re: Scala Code Generation
Date Wed, 14 Oct 2015 09:42:18 GMT
If you're using Scala, then you're bound to a maximum of 22 fields in a
tuple, because the Scala library does not provide larger tuples. You could
generate your own case classes which have more than the 22 fields, though.
On Oct 14, 2015 11:30 AM, "Ufuk Celebi" <uce@apache.org> wrote:

>
> > On 13 Oct 2015, at 16:06, schultze@informatik.hu-berlin.de wrote:
> >
> > Hello,
> >
> > I am currently working on a compilation unit translating AsterixDB's AQL
> > into runnable Scala code for Flink's Scala API. During code generation I
> > discovered some things that are quite hard to work around. I am still
> > working with Flink version 0.8, so some of the problems I have might
> > already be fixed in 0.9 and if so please tell me.
> >
> > First, whenever a record gets projected down to only a single field (e.g.
> > by a map or reduce function) it is no longer considered a record, but a
> > variable of the type of that field. If afterwards I want to apply
> > additional functions like .sum(0) I get an error message like
>
> A workaround is to return Tuple1<X> for this. Then you can run the
> aggregation. I think that the Tuple0 class has been added after 0.8 though.
>
> > "Aggregating on field positions is only possible on tuple data types."
> >
> > This is the same for all functions (like write or join) as the "record"
> is
> > no longer considered a dataset.
>
> What do you mean? At least in the current versions, the join projections
> return a Tuple type as well.
>
> > Second, I found that records longer than 22 fields are not supported.
> > Whenever I have a record that is longer than that I receive a build error
> > as
>
> Flink’s Tuple classes go up to Tuple25. You can work around this by using
> a custom PoJo type, e.g.
>
> class TPCHRecord {
>     public int f0;
>     ...
>     public int f99;
> }
>
> If possible, I would suggest to update to the latest 0.9 or the upcoming
> 0.10 release. A lot of stuff has been fixed since 0.8. I think it will be
> worth it. If you encounter any problems while doing this, feel free to ask
> here. :)
>
> – Ufuk

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