This looks like a good design to me :-) The only thing is that it is not complete. For example, the filter, mapPartition, coGroup and join functions are missing.
Cheers, Till On Tue, Feb 9, 2016 at 1:18 AM, Stefano Baghino < stefano.bagh...@radicalbit.io> wrote: > What do you think of something like this? > > > https://github.com/radicalbit/flink/commit/21a889a437875c88921c93e87d88a378c6b4299e > > In this way, several extensions can be collected in this package object and > picked altogether or a-là-carte (e.g. import > org.apache.flink.api.scala.extensions.AcceptPartialFunctions). > > On Mon, Feb 8, 2016 at 2:51 PM, Till Rohrmann <trohrm...@apache.org> > wrote: > > > I like the idea to support partial functions with Flink’s Scala API. > > However, I think that breaking the API and making it inconsistent with > > respect to the Java API is not the best option. I would rather be in > favour > > of the first proposal where we add a new method xxxWith via implicit > > conversions. > > > > Cheers, > > Till > > > > > > On Sun, Feb 7, 2016 at 12:44 PM, Stefano Baghino < > > stefano.bagh...@radicalbit.io> wrote: > > > > > It took me a little time but I was able to put together some code. > > > > > > In this commit I just added a few methods renamed to prevent > overloading, > > > thus usable with PartialFunction instead of functions: > > > > > > > > > https://github.com/radicalbit/flink/commit/aacd59e0ce98cccb66d48a30d07990ac8f345748 > > > > > > In this other commit I coded the original proposal, renaming the > methods > > to > > > obtain the same effect as before, but with lower friction for Scala > > > developers (and provided some usage examples): > > > > > > > > > https://github.com/radicalbit/flink/commit/33403878eebba70def42f73a1cb671d13b1521b5 > > > > > > On Thu, Jan 28, 2016 at 6:16 PM, Stefano Baghino < > > > stefano.bagh...@radicalbit.io> wrote: > > > > > > > Hi Stephan, > > > > > > > > thank you for the quick reply and for your feedback; I agree with you > > > that > > > > breaking changes have to taken very seriously. > > > > > > > > The rationale behind my proposal is that Scala users are already > > > > accustomed to higher-order functions that manipulate collections and > it > > > > would beneficial for them to have an API that tries to adhere as much > > as > > > > possible to the interface provided by the Scala Collections API. IMHO > > > being > > > > able to manipulate a DataSet or DataStream like a Scala collection > > > > idiomatically would appeal to developers and reduce the friction for > > them > > > > to learn Flink. > > > > > > > > If we want to pursue the renaming path, I think these changes (and > > > porting > > > > the rest of the codebase, like `flink-ml` and `flink-contrib`, to the > > new > > > > method names) can be done in relatively little time. Since Flink is > > > > approaching a major release, I think it's a good time to consider > this > > > > change, if the community deems it relevant. > > > > > > > > While we await for feedback on the proposal, I can start working on > > both > > > > paths to see how it would affect the codebase, what do you think? > > > > > > > > On Thu, Jan 28, 2016 at 2:14 PM, Stephan Ewen <se...@apache.org> > > wrote: > > > > > > > >> Hi! > > > >> > > > >> Would be nice to support that, agreed. > > > >> > > > >> Such a fundamental break in the API worries me a bit, though - I > would > > > opt > > > >> for a non-breaking addition. > > > >> Wrapping the RichFunctions into Scala functions (which are actually > > > >> wrapped > > > >> as rich functions) with implicits seems like a workaround for > > something > > > >> that should be very simple. Would probably also cost a bit of > > > performance. > > > >> > > > >> > > > >> I like the idea of "mapWith(...)" - if that were a simple non > > overloaded > > > >> function accepting a Scala function, it should accept case-style > > > >> functions, > > > >> right? > > > >> Simply adding that would probably solve things, but add a second > > variant > > > >> of > > > >> each function to the DataSet. An implicit conversion from DataSet to > > > >> DataSetExtended (which implements the mapWith, reduceWith, ...) > > methods > > > >> could help there... > > > >> > > > >> What do you think? > > > >> > > > >> Greetings, > > > >> Stephan > > > >> > > > >> > > > >> On Thu, Jan 28, 2016 at 2:05 PM, Stefano Baghino < > > > >> stefano.bagh...@radicalbit.io> wrote: > > > >> > > > >> > Hello everybody, > > > >> > > > > >> > as I'm getting familiar with Flink I've found a possible > improvement > > > to > > > >> the > > > >> > Scala APIs: in Scala it's a common pattern to perform tuple > > extraction > > > >> > using pattern matching, making functions working on tuples more > > > >> readable, > > > >> > like this: > > > >> > > > > >> > // referring to the mail count example in the training > > > >> > // assuming `mails` is a DataSet[(String, String)] > > > >> > // a pair of date and a string with username and email > > > >> > val monthsAndEmails = > > > >> > mails.map { > > > >> > case (date, sender) => > > > >> > (extractMonth(date), extractEmail(sender)) > > > >> > } > > > >> > > > > >> > However, this is not possible when using the Scala APIs because of > > the > > > >> > overloading of the `map` function in the `DataSet` and > `DataStream` > > > >> classes > > > >> > (along with other higher-order function such as `flatMap` and > > > >> `filter`). My > > > >> > understanding is that the main reason to have two different > > overloaded > > > >> > functions is to provide support for `RichFunction`s. > > > >> > I've found out there has been some interest around the issue in > the > > > >> past ( > > > >> > [FLINK-1159] <https://issues.apache.org/jira/browse/FLINK-1159>). > > > >> > In the past couple of days me and my colleague Andrea have tried > > > several > > > >> > ways to address the problem, coming to two possible solutions: > > > >> > > > > >> > 1. don't overload and use different names, e.g. `map` taking a > > > Scala > > > >> > function and `mapWith` taking a Flink MapFunction > > > >> > 2. keep only the method taking a Scala function (which would be > > > more > > > >> > idiomatic from a Scala perspective, IMHO) and providing an > > implicit > > > >> > conversion from the Flink function to the Scala function within > > the > > > >> > `org.apache.flink.api.scala` package object > > > >> > > > > >> > We've also evaluated several other approaches using union types > and > > > type > > > >> > classes but we've found them to be too complex. Regarding the two > > > >> > approaches I've cited, the first would imply a breaking change to > > the > > > >> APIs, > > > >> > while the second is giving me a hard time at figuring out some > > > >> compilation > > > >> > errors in `flink-libraries` and `flink-contrib` and as we tested > it > > we > > > >> > found out `RichMapFunction`s lose state (possibly because of the > > > double > > > >> > conversion, first to a Scala function, then to a simple > > > `MapFunction`). > > > >> > > > > >> > You can have a look at the code I've written so far here (last 2 > > > >> commits): > > > >> > https://github.com/radicalbit/flink/commits/1159 > > > >> > > > > >> > We had a little exchange of ideas and thought that the first > > solution > > > >> would > > > >> > be easier and also interesting from the standpoint of the > ergonomics > > > of > > > >> the > > > >> > API (e.g. `line mapWith new LineSplitter`) and would like to > gather > > > some > > > >> > feedback on the feasibility of this change. > > > >> > > > > >> > Would this still be regarded as a relevant improvement? What do > you > > > >> think > > > >> > about it? Do you think there's time to work on them before the 1.0 > > > >> release? > > > >> > What do you think about introducing breaking changes to make this > > > >> pattern > > > >> > available to Scala users? > > > >> > > > > >> > Thank you all in advance for your feedback. > > > >> > > > > >> > -- > > > >> > BR, > > > >> > Stefano Baghino > > > >> > > > > >> > Software Engineer @ Radicalbit > > > >> > > > > >> > > > > > > > > > > > > > > > > -- > > > > BR, > > > > Stefano Baghino > > > > > > > > Software Engineer @ Radicalbit > > > > > > > > > > > > > > > > -- > > > BR, > > > Stefano Baghino > > > > > > Software Engineer @ Radicalbit > > > > > > > > > -- > BR, > Stefano Baghino > > Software Engineer @ Radicalbit >
