Hey,
I have made a small prototype for a map-operator
env.fromElements(1, 2, 3)
.map((i) -> new Tuple2<String,String>()).returns("Tuple2<String,String>")
.print();
you can find my solution here:
https://github.com/twalthr/incubator-flink/commit/3ce2d3c86cf2457e02986f7a2d858304bbefea58
Actually, I like this solution most as it looks very easy to the user.
Furthermore, we can move the Type Extraction part into the operator
which makes more sense to me.
What do you think?
Greetings,
Timo
On 02.11.2014 16:22, Stephan Ewen wrote:
An alternative would be to go for
env.fromElements(1, 2, 3)
.flatMap((Integer i, Collector<Integer> o) -> o.collect(i) ,
returns("Integer"))
.print();
"returns" would here be a static method that creates the type info.
That would require to add an additional parameter, but allow us to keep the
immediate checks. Deferring the checks will make things harder to
understand for users as well...
Am 30.10.2014 11:44 schrieb "Stephan Ewen" <[email protected]>:
I think that would look nice.
How easy is that to implement? With that change, we could not initialize
the type info in the constructor any more, but would have to change
everything to lazy initialization, which makes it complicated and error
prone...
On Wed, Oct 29, 2014 at 4:26 PM, Timo Walther <[email protected]> wrote:
What do you think about something like:
env.fromElements(1, 2, 3)
.flatMap((Integer i, Collector<Integer> o) -> o.collect(i)).returns("
Integer")
.print();
This looks to me like the most readable and user-friendly solution. We
only need to change the internals of DataSet a little bit, such that a
possible TypeExtractor Exception is stored temporarily and thrown by the
operator that follows if "returns()" was not called.
Regards,
Timo
On 28.10.2014 15:34, Stephan Ewen wrote:
Is it possible to use a static method "hint" to create the hinting wrapper
function?
Something like
DataSet.map(hint( (x) -> x.toString() , String.class));
If we go for option (1), I would suggest to call the methods just "from"
and overload them for String, Class, and TypeInformation
Stephan
On Tue, Oct 28, 2014 at 3:27 PM, Timo Walther <[email protected]> wrote:
Hi all,
currently the Eclipse JDT compiler was the only compiler that included
generic signatures for Lambda Expressions in class files which is
necessary
to use them type-safe in Flink. Unfortunalely, this "feature" was
considered as a "bug" and had been thrown out with Eclipse 4.4.1. This is
why Lambdas do not work properly with the current version of Eclipse. I
have opened a bug for that (see https://bugs.eclipse.org/bugs/
show_bug.cgi?id=449063).
The question is: Independent of the decision of the Eclipse JDT team, how
do we want to deal with missing return type information?
Option 1)
Add a separate TypeInformation argument to each Java API operator. Leads
to blown up API...
.map((x)->x + 1, TypeInformation.fromString("Integer"))
.flatMap((in, out)->out.collect(in), TypeInformation.fromClass(
Integer.class))
Option 2)
Introduce a wrapper class which implements ResultTypeQueryable. Leads to
complicated syntax...
.map(TypeHint.map((x)->x + 1, "Integer"));
.map(TypeHint.map((x)->x + 1, Integer.class));
What are your opinions? Or any other ideas?
Regards,
Timo
