Sorry I'm not sure what your last email means. Does it mean you are putting it
up for a vote or just waiting to get more feedback? I disagree with saying
option 4 is the rule but agree having a general rule makes sense. I think we
need a lot more input to make the rule as it affects the api's.
Tom
On Wednesday, April 29, 2020, 09:53:22 AM CDT, Hyukjin Kwon
<gurwls...@gmail.com> wrote:
I think I am not seeing explicit objection here but rather see people tend to
agree with the proposal in general.
I would like to step forward rather than leaving it as a deadlock - the worst
choice here is to postpone and abandon this discussion with this inconsistency.
I don't currently target to document this as the cases are rather rare, and we
haven't really documented JavaRDD <> RDD vs DataFrame case as well.
Let's keep monitoring and see if this discussion thread clarifies things enough
in such cases I mentioned.
Let me know if you guys think differently.
2020년 4월 28일 (화) 오후 5:03, Hyukjin Kwon <gurwls...@gmail.com>님이 작성:
Spark has targeted to have a unified API set rather than having separate Java
classes to reduce the maintenance cost,
e.g.) JavaRDD <> RDD vs DataFrame. These JavaXXX are more about the legacy.
I think it's best to stick to the approach 4. in general cases.
Other options might have to be considered based upon a specific context. For
example, if we must to add a bunch of Java-specifics
into a specific class for an inevitable reason somewhere, I would consider to
have a Java-specific class.
2020년 4월 28일 (화) 오후 4:38, ZHANG Wei <wezh...@outlook.com>님이 작성:
Be frankly, I also love the pure Java type in Java API and Scala type in
Scala API. :-)
If we don't treat Java as a "FRIEND" of Scala, just as Python, maybe we
can adopt the status of option 1, the specific Java classes. (But I don't
like the `Java` prefix, which is redundant when I'm coding Java app,
such as JavaRDD, why not distinct it by package namespace...) The specific
Java API can also leverage some native Java language features with new
versions.
And just since the friendly relationship between Scala and Java, the Java
user can call Scala API with `.asScala` or `.asJava`'s help if Java API
is not ready. Then switch to Java API when it's well cooked.
The cons is more efforts to maintain.
My 2 cents.
--
Cheers,
-z
On Tue, 28 Apr 2020 12:07:36 +0900
Hyukjin Kwon <gurwls...@gmail.com> wrote:
> The problem is that calling Scala instances in Java side is discouraged in
> general up to my best knowledge.
> A Java user won't likely know asJava in Scala but a Scala user will likely
> know both asScala and asJava.
>
>
> 2020년 4월 28일 (화) 오전 11:35, ZHANG Wei <wezh...@outlook.com>님이 작성:
>
> > How about making a small change on option 4:
> > Keep Scala API returning Scala type instance with providing a
> > `asJava` method to return a Java type instance.
> >
> > Scala 2.13 has provided CollectionConverter [1][2][3], in the following
> > Spark dependences upgrade, which can be supported by nature. For
> > current Scala 2.12 version, we can wrap `ImplicitConversionsToJava`[4]
> > as what Scala 2.13 does and add implicit conversions.
> >
> > Just my 2 cents.
> >
> > --
> > Cheers,
> > -z
> >
> > [1]
> > https://nam11.safelinks.protection.outlook.com/?url=https%3A%2F%2Fdocs.scala-lang.org%2Foverviews%2Fcollections-2.13%2Fconversions-between-java-and-scala-collections.html&data=02%7C01%7C%7C7f0d8171d15848afb10c08d7eb215530%7C84df9e7fe9f640afb435aaaaaaaaaaaa%7C1%7C0%7C637236400701707166&sdata=1qauveOMB1lKHSkRco7v8tBpcJXab8IeGlcoYNMCZ%2BU%3D&reserved=0
> > [2]
> > https://nam11.safelinks.protection.outlook.com/?url=https%3A%2F%2Fwww.scala-lang.org%2Fapi%2F2.13.0%2Fscala%2Fjdk%2Fjavaapi%2FCollectionConverters%24.html&data=02%7C01%7C%7C7f0d8171d15848afb10c08d7eb215530%7C84df9e7fe9f640afb435aaaaaaaaaaaa%7C1%7C0%7C637236400701707166&sdata=%2B9TrlfiGSWDnsaT8DMPrSn1CqGIxtgfNLcPFRJ%2F%2FANQ%3D&reserved=0
> > [3]
> > https://nam11.safelinks.protection.outlook.com/?url=https%3A%2F%2Fwww.scala-lang.org%2Fapi%2F2.13.0%2Fscala%2Fjdk%2FCollectionConverters%24.html&data=02%7C01%7C%7C7f0d8171d15848afb10c08d7eb215530%7C84df9e7fe9f640afb435aaaaaaaaaaaa%7C1%7C0%7C637236400701707166&sdata=EjocqFcoIho43wU3yvOEO9Vtvn2jTHliV88W%2BSOed9k%3D&reserved=0
> > [4]
> > https://nam11.safelinks.protection.outlook.com/?url=https%3A%2F%2Fwww.scala-lang.org%2Fapi%2F2.12.11%2Fscala%2Fcollection%2Fconvert%2FImplicitConversionsToJava%24.html&data=02%7C01%7C%7C7f0d8171d15848afb10c08d7eb215530%7C84df9e7fe9f640afb435aaaaaaaaaaaa%7C1%7C0%7C637236400701707166&sdata=BpMYD30%2B2tXeaoIj0nNhlho8XUZOEYvT%2FzH%2FJ4WEK98%3D&reserved=0
> >
> >
> > On Tue, 28 Apr 2020 08:52:57 +0900
> > Hyukjin Kwon <gurwls...@gmail.com> wrote:
> >
> > > I would like to make sure I am open for other options that can be
> > > considered situationally and based on the context.
> > > It's okay, and I don't target to restrict this here. For example, DSv2, I
> > > understand it's written in Java because Java
> > > interfaces arguably brings better performance. That's why vectorized
> > > readers are written in Java too.
> > >
> > > Maybe the "general" wasn't explicit in my previous email. Adding APIs to
> > > return a Java instance is still
> > > rather rare in general given my few years monitoring.
> > > The problem I would more like to deal with is more about when we need to
> > > add one or a couple of user-facing
> > > Java-specific APIs to return Java instances, which is relatively more
> > > frequent compared to when we need a bunch
> > > of Java specific APIs.
> > >
> > > In this case, I think it should be guided to use 4. approach. There are
> > > pros and cons between 3. and 4., of course.
> > > But it looks to me 4. approach is closer to what Spark has targeted so
> > far.
> > >
> > >
> > >
> > > 2020년 4월 28일 (화) 오전 8:34, Hyukjin Kwon <gurwls...@gmail.com>님이 작성:
> > >
> > > > > One thing we could do here is use Java collections internally and
> > make
> > > > the Scala API a thin wrapper around Java -- like how Python works.
> > > > > Then adding a method to the Scala API would require adding it to the
> > > > Java API and we would keep the two more in sync.
> > > >
> > > > I think it can be an appropriate idea for when we have to deal with
> > this
> > > > case a lot but I don't think there are so many
> > > > user-facing APIs to return a Java collections, it's rather rare. Also,
> > the
> > > > Java users are relatively less than Scala users.
> > > > This case is slightly different from Python in a way that there are so
> > > > many differences to deal with in PySpark case.
> > > >
> > > > Also, in case of `Seq`, actually we can just use `Array` instead for
> > both
> > > > Scala and Java side simply. I don't find such cases notably awkward.
> > > > This problematic cases might be specific to few Java collections or
> > > > instances, and I would like to avoid an overkill here.
> > > >
> > > > Of course, if there is a place to consider other options, let's do. I
> > > > don't like to say this is the only required option.
> > > >
> > > >
> > > >
> > > >
> > > >
> > > > 2020년 4월 28일 (화) 오전 1:18, Ryan Blue <rb...@netflix.com.invalid>님이 작성:
> > > >
> > > >> I think the right choice here depends on how the object is used. For
> > > >> developer and internal APIs, I think standardizing on Java collections
> > > >> makes the most sense.
> > > >>
> > > >> For user-facing APIs, it is awkward to return Java collections to
> > Scala
> > > >> code -- I think that's the motivation for Tom's comment. For user
> > APIs, I
> > > >> think most methods should return Scala collections, and I don't have a
> > > >> strong opinion about whether the conversion (or lack thereof) is done
> > in a
> > > >> separate object (#1) or in parallel methods (#3).
> > > >>
> > > >> Both #1 and #3 seem like about the same amount of work and have the
> > same
> > > >> likelihood that a developer will leave out a Java method version. One
> > thing
> > > >> we could do here is use Java collections internally and make the
> > Scala API
> > > >> a thin wrapper around Java -- like how Python works. Then adding a
> > method
> > > >> to the Scala API would require adding it to the Java API and we would
> > keep
> > > >> the two more in sync. It would also help avoid Scala collections
> > leaking
> > > >> into internals.
> > > >>
> > > >> On Mon, Apr 27, 2020 at 8:49 AM Hyukjin Kwon <gurwls...@gmail.com>
> > wrote:
> > > >>
> > > >>> Let's stick to the less maintenance efforts then rather than we
> > leave it
> > > >>> undecided and delay with leaving this inconsistency.
> > > >>>
> > > >>> I dont think we can have some very meaningful data about this soon
> > given
> > > >>> that we don't hear much complaints about this in general so far.
> > > >>>
> > > >>> The point of this thread is to make a call rather then defer to the
> > > >>> future.
> > > >>>
> > > >>> On Mon, 27 Apr 2020, 23:15 Wenchen Fan, <cloud0...@gmail.com> wrote:
> > > >>>
> > > >>>> IIUC We are moving away from having 2 classes for Java and Scala,
> > like
> > > >>>> JavaRDD and RDD. It's much simpler to maintain and use with a
> > single class.
> > > >>>>
> > > >>>> I don't have a strong preference over option 3 or 4. We may need to
> > > >>>> collect more data points from actual users.
> > > >>>>
> > > >>>> On Mon, Apr 27, 2020 at 9:50 PM Hyukjin Kwon <gurwls...@gmail.com>
> > > >>>> wrote:
> > > >>>>
> > > >>>>> Scala users are arguably more prevailing compared to Java users,
> > yes.
> > > >>>>> Using the Java instances in Scala side is legitimate, and they are
> > > >>>>> already being used in multiple please. I don't believe Scala
> > > >>>>> users find this not Scala friendly as it's legitimate and already
> > > >>>>> being used. I personally find it's more trouble some to let Java
> > > >>>>> users to search which APIs to call. Yes, I understand the pros and
> > > >>>>> cons - we should also find the balance considering the actual
> > usage.
> > > >>>>>
> > > >>>>> One more argument from me is, though, I think one of the goals in
> > > >>>>> Spark APIs is the unified API set up to my knowledge
> > > >>>>> e.g., JavaRDD <> RDD vs DataFrame.
> > > >>>>> If either way is not particularly preferred over the other, I would
> > > >>>>> just choose the one to have the unified API set.
> > > >>>>>
> > > >>>>>
> > > >>>>>
> > > >>>>> 2020년 4월 27일 (월) 오후 10:37, Tom Graves <tgraves...@yahoo.com>님이 작성:
> > > >>>>>
> > > >>>>>> I agree a general guidance is good so we keep consistent in the
> > apis.
> > > >>>>>> I don't necessarily agree that 4 is the best solution though. I
> > agree its
> > > >>>>>> nice to have one api, but it is less friendly for the scala side.
> > > >>>>>> Searching for the equivalent Java api shouldn't be hard as it
> > should be
> > > >>>>>> very close in the name and if we make it a general rule users
> > should
> > > >>>>>> understand it. I guess one good question is what API do most of
> > our users
> > > >>>>>> use between Java and Scala and what is the ratio? I don't know
> > the answer
> > > >>>>>> to that. I've seen more using Scala over Java. If the majority
> > use Scala
> > > >>>>>> then I think the API should be more friendly to that.
> > > >>>>>>
> > > >>>>>> Tom
> > > >>>>>>
> > > >>>>>> On Monday, April 27, 2020, 04:04:28 AM CDT, Hyukjin Kwon <
> > > >>>>>> gurwls...@gmail.com> wrote:
> > > >>>>>>
> > > >>>>>>
> > > >>>>>> Hi all,
> > > >>>>>>
> > > >>>>>> I would like to discuss Java specific APIs and which design we
> > will
> > > >>>>>> choose.
> > > >>>>>> This has been discussed in multiple places so far, for example, at
> > > >>>>>> https://nam11.safelinks.protection.outlook.com/?url=https%3A%2F%2Fgithub.com%2Fapache%2Fspark%2Fpull%2F28085%23discussion_r407334754&data=02%7C01%7C%7C7f0d8171d15848afb10c08d7eb215530%7C84df9e7fe9f640afb435aaaaaaaaaaaa%7C1%7C0%7C637236400701707166&sdata=6A82CT7n4FwG6f1Hx3%2FqmetQVSGWlrcE7BHDx0LLwTo%3D&reserved=0
> > > >>>>>>
> > > >>>>>>
> > > >>>>>> *The problem:*
> > > >>>>>>
> > > >>>>>> In short, I would like us to have clear guidance on how we support
> > > >>>>>> Java specific APIs when
> > > >>>>>> it requires to return a Java instance. The problem is simple:
> > > >>>>>>
> > > >>>>>> def requests: Map[String, ExecutorResourceRequest] = ...
> > > >>>>>> def requestsJMap: java.util.Map[String, ExecutorResourceRequest]
> > = ...
> > > >>>>>>
> > > >>>>>> vs
> > > >>>>>>
> > > >>>>>> def requests: java.util.Map[String, ExecutorResourceRequest] = ...
> > > >>>>>>
> > > >>>>>>
> > > >>>>>> *Current codebase:*
> > > >>>>>>
> > > >>>>>> My understanding so far was that the latter is preferred and more
> > > >>>>>> consistent and prevailing in the
> > > >>>>>> existing codebase, for example, see StateOperatorProgress and
> > > >>>>>> StreamingQueryProgress in Structured Streaming.
> > > >>>>>> However, I realised that we also have other approaches in the
> > current
> > > >>>>>> codebase. There look
> > > >>>>>> four approaches to deal with Java specifics in general:
> > > >>>>>>
> > > >>>>>> 1. Java specific classes such as JavaRDD and JavaSparkContext.
> > > >>>>>> 2. Java specific methods with the same name that overload its
> > > >>>>>> parameters, see functions.scala.
> > > >>>>>> 3. Java specific methods with a different name that needs to
> > > >>>>>> return a different type such as TaskContext.resourcesJMap vs
> > > >>>>>> TaskContext.resources.
> > > >>>>>> 4. One method that returns a Java instance for both Scala and
> > > >>>>>> Java sides. see StateOperatorProgress and
> > StreamingQueryProgress.
> > > >>>>>>
> > > >>>>>>
> > > >>>>>> *Analysis on the current codebase:*
> > > >>>>>>
> > > >>>>>> I agree with 2. approach because the corresponding cases give you
> > a
> > > >>>>>> consistent API usage across
> > > >>>>>> other language APIs in general. Approach 1. is from the old world
> > > >>>>>> when we didn't have unified APIs.
> > > >>>>>> This might be the worst approach.
> > > >>>>>>
> > > >>>>>> 3. and 4. are controversial.
> > > >>>>>>
> > > >>>>>> For 3., if you have to use Java APIs, then, you should search if
> > > >>>>>> there is a variant of that API
> > > >>>>>> every time specifically for Java APIs. But yes, it gives you
> > > >>>>>> Java/Scala friendly instances.
> > > >>>>>>
> > > >>>>>> For 4., having one API that returns a Java instance makes you
> > able to
> > > >>>>>> use it in both Scala and Java APIs
> > > >>>>>> sides although it makes you call asScala in Scala side
> > specifically.
> > > >>>>>> But you don’t
> > > >>>>>> have to search if there’s a variant of this API and it gives you a
> > > >>>>>> consistent API usage across languages.
> > > >>>>>>
> > > >>>>>> Also, note that calling Java in Scala is legitimate but the
> > opposite
> > > >>>>>> case is not, up to my best knowledge.
> > > >>>>>> In addition, you should have a method that returns a Java instance
> > > >>>>>> for PySpark or SparkR to support.
> > > >>>>>>
> > > >>>>>>
> > > >>>>>> *Proposal:*
> > > >>>>>>
> > > >>>>>> I would like to have a general guidance on this that the Spark dev
> > > >>>>>> agrees upon: Do 4. approach. If not possible, do 3. Avoid 1
> > almost at all
> > > >>>>>> cost.
> > > >>>>>>
> > > >>>>>> Note that this isn't a hard requirement but *a general guidance*;
> > > >>>>>> therefore, the decision might be up to
> > > >>>>>> the specific context. For example, when there are some strong
> > > >>>>>> arguments to have a separate Java specific API, that’s fine.
> > > >>>>>> Of course, we won’t change the existing methods given Micheal’s
> > > >>>>>> rubric added before. I am talking about new
> > > >>>>>> methods in unreleased branches.
> > > >>>>>>
> > > >>>>>> Any concern or opinion on this?
> > > >>>>>>
> > > >>>>>
> > > >>
> > > >> --
> > > >> Ryan Blue
> > > >> Software Engineer
> > > >> Netflix
> > > >>
> > > >
> >
