I'd suggest we do not block this KIP until the serde work has been sorted
out: we cannot estimate yet how long it will take yet. Instead let's say
make an agreement on where we want to specify the serdes: whether on the
first co-group call or on the aggregate call.
Also about the initializer specification I actually felt that the first
cogrouped stream is special (Kyle please feel free to correct me if I'm
wrong) and that is why I thought it is better to specify the initializer at
the beginning: since from the typing you can see that the final aggregated
value type is defined to be the same as the first co-grouped stream, and
for any intermediate stream to co-group, their value types not be inherited
but the value be "incorporated" into the original stream:
<T> CogroupedKStream<K, V> cogroup(final KGroupedStream<K, T>
groupedStream, final Aggregator<? super K, ? super T, V> aggregator)
Note that we do not have a cogroup function that returns
CogroupedKStream<K, T>.
Guozhang
On Tue, Jun 13, 2017 at 2:31 PM, Bill Bejeck <bbej...@gmail.com> wrote:
> +1 on deferring discussion on Serdes until API improvements are ironed out.
>
> On Tue, Jun 13, 2017 at 2:06 PM, Matthias J. Sax <matth...@confluent.io>
> wrote:
>
> > Hi,
> >
> > I am just catching up on this thread. (1) as most people agree, we
> > should not add anything to KStreamBuilder (btw: we actually plan to move
> > #merge() to KStream and deprecate it on KStreamBuilder as it's a quite
> > unnatural API atm).
> >
> > About specifying Serdes: there is still the idea to improve to overall
> > API from the current "we are adding more overloads"-pattern to a
> > builder-like pattern. This might make the whole discussion void if we do
> > this. Thus, it might make sense to keep this in mind (or even delay this
> > KIP?). It seems a waste of time to discuss all this if we are going to
> > chance it in 2 month anyway... Just saying.
> >
> >
> > -Matthias
> >
> > On 6/13/17 8:05 AM, Michal Borowiecki wrote:
> > > You're right, I haven't thought of that.
> > >
> > > Cheers,
> > >
> > > Michał
> > >
> > >
> > > On 13/06/17 13:00, Kyle Winkelman wrote:
> > >> First, I would prefer not calling it aggregate because there are
> already
> > >> plenty of aggregate methods.
> > >>
> > >> Second, I dont think this would really work because after each
> aggregate
> > >> you now have a unique KTable (someone may want a table with 4 streams
> > and
> > >> reuse those 4 in another table but with one more stream added) and
> > unless
> > >> we completely duplicate everything every time this isnt really
> possible.
> > >> Additionally, the cogroup way just requires 1 more call to create two
> > >> different tables (normal, windowed, and session windowed) this new way
> > >> would require copying the aggregate chain.
> > >>
> > >> Another way to think about it is with cogroup we know that when they
> > call
> > >> aggregate they arent going to be adding any more aggregators to that
> > table
> > >> but your way requires us to assume they are done adding aggregators
> > after
> > >> each call so we must return a ktable just to possibly not need to have
> > >> created it.
> > >>
> > >> On Jun 13, 2017 5:20 AM, "Michal Borowiecki" <
> > michal.borowie...@openbet.com>
> > >> wrote:
> > >>
> > >>> Actually, just had a thought. It started with naming.
> > >>>
> > >>> Are we actually co-grouping these streams or are we co-aggregating
> > them?
> > >>>
> > >>> After all, in each of the cogroup calls we are providing an
> Aggregator
> > >>> implementation.
> > >>>
> > >>>
> > >>> If they are really co-aggregated, why don't we turn this around:
> > >>> KGroupedStream<K, V1> grouped1 = builder.stream("topic1").
> > groupByKey();
> > >>> KGroupedStream<K, V2> grouped2 = builder.stream("topic2").
> > groupByKey();
> > >>> KGroupedStream<K, V3> grouped3 = builder.stream("topic3").
> > groupByKey();
> > >>>
> > >>> KTable<K, CG> coagg = grouped1.aggregate(initializer1, aggregator1,
> > >>> aggValueSerde1) // this is the unchanged aggregate method
> > >>> .aggregate(grouped2, aggregator2) // this is a new method
> > >>> .aggregate(grouped3, aggregator3); // ditto
> > >>>
> > >>> This means instead of adding cogroup methods on KGroupStream
> interface,
> > >>> adding aggregate method on KTable interface.
> > >>>
> > >>> Is that feasible?
> > >>>
> > >>> Cheers,
> > >>> Michał
> > >>>
> > >>> On 13/06/17 10:56, Michal Borowiecki wrote:
> > >>>
> > >>> Also, I still feel that putting initializer on the first cogroup can
> > >>> mislead users into thinking the first stream is in some way special.
> > >>> Just my 5c.
> > >>> Michał
> > >>>
> > >>> On 13/06/17 09:54, Michal Borowiecki wrote:
> > >>>
> > >>> Agree completely with the argument for serdes belonging in the same
> > place
> > >>> as the state store name, which is in the aggregate method.
> > >>>
> > >>> Cheers,
> > >>>
> > >>> Michał
> > >>>
> > >>> On 12/06/17 18:20, Xavier Léauté wrote:
> > >>>
> > >>> I think we are discussing two separate things here, so it might be
> > worth
> > >>> clarifying:
> > >>>
> > >>> 1) the position of the initializer with respect to the aggregators.
> If
> > I
> > >>> understand correctly, Guozhang seems to think it is more natural to
> > specify
> > >>> the initializer first, despite it not bearing any relation to the
> first
> > >>> aggregator. I can see the argument for specifying the initializer
> > first,
> > >>> but I think it is debatable whether mixing it into the first cogroup
> > call
> > >>> leads to a cleaner API or not.
> > >>>
> > >>> 2) where the serde should be defined (if necessary). Looking at our
> > >>> existing APIs in KGroupedStreams, we always offer two aggregate()
> > >>> methods. The first one takes the name of the store and associated
> > aggregate
> > >>> value serde e.g. KGroupedStream.aggregate(Initializer<VR>
> initializer,
> > >>> Aggregator<? super K, ? super V, VR> aggregator, Serde<VR>
> > aggValueSerde,
> > >>> String queryableStoreName)
> > >>> The second one only takes a state store supplier, and does not
> specify
> > any
> > >>> serde, e.g. KGroupedStream.aggregate(Initializer<VR>
> > >>> initializer, Aggregator<? super K, ? super V, VR> aggregator, final
> > >>> StateStoreSupplier<KeyValueStore> storeSupplier)
> > >>> Presumably, when specifying a state store supplier it shouldn't be
> > >>> necessary to specify an aggregate value serde, since the provided
> > >>> statestore might not need to serialize the values (e.g. it may just
> > keep
> > >>> them as regular objects in heap) or it may have its own
> > >>> internal serialization format.
> > >>>
> > >>> For consistency I think it would be valuable to preserve the same two
> > >>> aggregate methods for cogroup as well. Since the serde is only
> > required in
> > >>> one of the two cases, I believe the serde has no place in the first
> > >>> cogroup() call and should only have to be specified as part of the
> > >>> aggregate() method that takes a state store name. In the case of a
> > state
> > >>> store supplier, no serde would be necessary.
> > >>>
> > >>>
> > >>> On Sat, Jun 10, 2017 at 4:09 PM Guozhang Wang <wangg...@gmail.com>
> > wrote:
> > >>>
> > >>>> I'd agree that the aggregate value serde and the initializer does
> not
> > >>>> bear direct relationship with the first `cogroup` calls, but after I
> > tried
> > >>>> to write some example code with these two different set of APIs I
> > felt the
> > >>>> current APIs just program more naturally.
> > >>>>
> > >>>> I know it is kinda subjective, but I do think that user experience
> > may be
> > >>>> more important as a deciding factor than the logical argument for
> > public
> > >>>> interfaces. So I'd recommend people to also try out writing some
> > example
> > >>>> lines also and we can circle back and discuss which one feels more
> > natural
> > >>>> to write code.
> > >>>>
> > >>>>
> > >>>> Guozhang
> > >>>>
> > >>>> On Fri, Jun 9, 2017 at 1:59 AM, Michal Borowiecki <
> > >>>> michal.borowie...@openbet.com> wrote:
> > >>>>
> > >>>>> I feel it would make more sense to move the initializer and serde
> to
> > the
> > >>>>> final aggregate statement, since the serde only applies to the
> state
> > >>>>> store,
> > >>>>> and the initializer doesn't bear any relation to the first group in
> > >>>>> particular.
> > >>>>>
> > >>>>> +1 for moving initializer and serde from cogroup() to the
> aggregate()
> > >>>>> for the reasons mentioned above.
> > >>>>>
> > >>>>> Cheers,
> > >>>>>
> > >>>>> Michał
> > >>>>>
> > >>>>> On 08/06/17 22:44, Guozhang Wang wrote:
> > >>>>>
> > >>>> Note that although the internal `AbstractStoreSupplier` does
> maintain
> > the
> > >>>>> key-value serdes, we do not enforce the interface of
> > `StateStoreSupplier`
> > >>>>> to always retain that information, and hence we cannot assume that
> > >>>>> StateStoreSuppliers always retain key / value serdes.
> > >>>>>
> > >>>>> On Thu, Jun 8, 2017 at 11:51 AM, Xavier Léauté <
> xav...@confluent.io>
> > <xav...@confluent.io> wrote:
> > >>>>>
> > >>>>>
> > >>>>> Another reason for the serde not to be in the first cogroup call,
> is
> > that
> > >>>>> the serde should not be required if you pass a StateStoreSupplier
> to
> > >>>>> aggregate()
> > >>>>>
> > >>>>> Regarding the aggregated type <T> I don't the why initializer
> should
> > be
> > >>>>> favored over aggregator to define the type. In my mind separating
> the
> > >>>>> initializer into the last aggregate call clearly indicates that the
> > >>>>> initializer is independent of any of the aggregators or streams and
> > that we
> > >>>>> don't wait for grouped1 events to initialize the co-group.
> > >>>>>
> > >>>>> On Thu, Jun 8, 2017 at 11:14 AM Guozhang Wang <wangg...@gmail.com>
> <
> > wangg...@gmail.com> wrote:
> > >>>>>
> > >>>>>
> > >>>>> On a second thought... This is the current proposal API
> > >>>>>
> > >>>>>
> > >>>>> ```
> > >>>>>
> > >>>>> <T> CogroupedKStream<K, T> cogroup(final Initializer<T>
> initializer,
> > >>>>>
> > >>>>> final
> > >>>>>
> > >>>>> Aggregator<? super K, ? super V, T> aggregator, final Serde<T>
> > >>>>> aggValueSerde)
> > >>>>>
> > >>>>> ```
> > >>>>>
> > >>>>>
> > >>>>> If we do not have the initializer in the first co-group it might be
> > a bit
> > >>>>> awkward for users to specify the aggregator that returns a typed
> <T>
> > >>>>>
> > >>>>> value?
> > >>>>>
> > >>>>> Maybe it is still better to put these two functions in the same
> api?
> > >>>>>
> > >>>>>
> > >>>>>
> > >>>>> Guozhang
> > >>>>>
> > >>>>> On Thu, Jun 8, 2017 at 11:08 AM, Guozhang Wang <wangg...@gmail.com
> >
> > <wangg...@gmail.com>
> > >>>>>
> > >>>>> wrote:
> > >>>>>
> > >>>>> This suggestion lgtm. I would vote for the first alternative than
> > >>>>>
> > >>>>> adding
> > >>>>>
> > >>>>> it to the `KStreamBuilder` though.
> > >>>>>
> > >>>>> On Thu, Jun 8, 2017 at 10:58 AM, Xavier Léauté <
> xav...@confluent.io>
> > <xav...@confluent.io>
> > >>>>> wrote:
> > >>>>>
> > >>>>>
> > >>>>> I have a minor suggestion to make the API a little bit more
> > symmetric.
> > >>>>> I feel it would make more sense to move the initializer and serde
> to
> > >>>>>
> > >>>>> the
> > >>>>>
> > >>>>> final aggregate statement, since the serde only applies to the
> state
> > >>>>> store,
> > >>>>> and the initializer doesn't bear any relation to the first group in
> > >>>>> particular. It would end up looking like this:
> > >>>>>
> > >>>>> KTable<K, CG> cogrouped =
> > >>>>> grouped1.cogroup(aggregator1)
> > >>>>> .cogroup(grouped2, aggregator2)
> > >>>>> .cogroup(grouped3, aggregator3)
> > >>>>> .aggregate(initializer1, aggValueSerde, storeName1);
> > >>>>>
> > >>>>> Alternatively, we could move the the first cogroup() method to
> > >>>>> KStreamBuilder, similar to how we have .merge()
> > >>>>> and end up with an api that would be even more symmetric.
> > >>>>>
> > >>>>> KStreamBuilder.cogroup(grouped1, aggregator1)
> > >>>>> .cogroup(grouped2, aggregator2)
> > >>>>> .cogroup(grouped3, aggregator3)
> > >>>>> .aggregate(initializer1, aggValueSerde, storeName1);
> > >>>>>
> > >>>>> This doesn't have to be a blocker, but I thought it would make the
> > API
> > >>>>> just
> > >>>>> a tad cleaner.
> > >>>>>
> > >>>>> On Tue, Jun 6, 2017 at 3:59 PM Guozhang Wang <wangg...@gmail.com>
> <
> > wangg...@gmail.com>
> > >>>>>
> > >>>>> wrote:
> > >>>>>
> > >>>>> Kyle,
> > >>>>>
> > >>>>> Thanks a lot for the updated KIP. It looks good to me.
> > >>>>>
> > >>>>>
> > >>>>> Guozhang
> > >>>>>
> > >>>>>
> > >>>>> On Fri, Jun 2, 2017 at 5:37 AM, Jim Jagielski <j...@jagunet.com> <
> > j...@jagunet.com>
> > >>>>>
> > >>>>> wrote:
> > >>>>>
> > >>>>> This makes much more sense to me. +1
> > >>>>>
> > >>>>>
> > >>>>> On Jun 1, 2017, at 10:33 AM, Kyle Winkelman <
> > >>>>>
> > >>>>> winkelman.k...@gmail.com>
> > >>>>>
> > >>>>> wrote:
> > >>>>>
> > >>>>> I have updated the KIP and my PR. Let me know what you think.
> > >>>>> To created a cogrouped stream just call cogroup on a
> > >>>>>
> > >>>>> KgroupedStream
> > >>>>>
> > >>>>> and
> > >>>>>
> > >>>>> supply the initializer, aggValueSerde, and an aggregator. Then
> > >>>>>
> > >>>>> continue
> > >>>>>
> > >>>>> adding kgroupedstreams and aggregators. Then call one of the
> > >>>>>
> > >>>>> many
> > >>>>>
> > >>>>> aggregate
> > >>>>>
> > >>>>> calls to create a KTable.
> > >>>>>
> > >>>>> Thanks,
> > >>>>> Kyle
> > >>>>>
> > >>>>> On Jun 1, 2017 4:03 AM, "Damian Guy" <damian....@gmail.com> <
> > damian....@gmail.com>
> > >>>>>
> > >>>>> wrote:
> > >>>>>
> > >>>>> Hi Kyle,
> > >>>>>
> > >>>>> Thanks for the update. I think just one initializer makes sense
> > >>>>>
> > >>>>> as
> > >>>>>
> > >>>>> it
> > >>>>>
> > >>>>> should only be called once per key and generally it is just
> > >>>>>
> > >>>>> going
> > >>>>>
> > >>>>> to
> > >>>>>
> > >>>>> create
> > >>>>>
> > >>>>> a new instance of whatever the Aggregate class is.
> > >>>>>
> > >>>>> Cheers,
> > >>>>> Damian
> > >>>>>
> > >>>>> On Wed, 31 May 2017 at 20:09 Kyle Winkelman <
> > >>>>>
> > >>>>> winkelman.k...@gmail.com
> > >>>>>
> > >>>>> wrote:
> > >>>>>
> > >>>>>
> > >>>>> Hello all,
> > >>>>>
> > >>>>> I have spent some more time on this and the best alternative I
> > >>>>>
> > >>>>> have
> > >>>>>
> > >>>>> come
> > >>>>>
> > >>>>> up
> > >>>>>
> > >>>>> with is:
> > >>>>> KGroupedStream has a single cogroup call that takes an
> > >>>>>
> > >>>>> initializer
> > >>>>>
> > >>>>> and
> > >>>>>
> > >>>>> an
> > >>>>>
> > >>>>> aggregator.
> > >>>>> CogroupedKStream has a cogroup call that takes additional
> > >>>>>
> > >>>>> groupedStream
> > >>>>>
> > >>>>> aggregator pairs.
> > >>>>> CogroupedKStream has multiple aggregate methods that create
> > >>>>>
> > >>>>> the
> > >>>>>
> > >>>>> different
> > >>>>>
> > >>>>> stores.
> > >>>>>
> > >>>>> I plan on updating the kip but I want people's input on if we
> > >>>>>
> > >>>>> should
> > >>>>>
> > >>>>> have
> > >>>>>
> > >>>>> the initializer be passed in once at the beginning or if we
> > >>>>>
> > >>>>> should
> > >>>>>
> > >>>>> instead
> > >>>>>
> > >>>>> have the initializer be required for each call to one of the
> > >>>>>
> > >>>>> aggregate
> > >>>>>
> > >>>>> calls. The first makes more sense to me but doesnt allow the
> > >>>>>
> > >>>>> user
> > >>>>>
> > >>>>> to
> > >>>>>
> > >>>>> specify different initializers for different tables.
> > >>>>>
> > >>>>> Thanks,
> > >>>>> Kyle
> > >>>>>
> > >>>>> On May 24, 2017 7:46 PM, "Kyle Winkelman" <
> > >>>>>
> > >>>>> winkelman.k...@gmail.com>
> > >>>>>
> > >>>>> wrote:
> > >>>>>
> > >>>>>
> > >>>>> Yea I really like that idea I'll see what I can do to update
> > >>>>>
> > >>>>> the
> > >>>>>
> > >>>>> kip
> > >>>>>
> > >>>>> and
> > >>>>>
> > >>>>> my pr when I have some time. I'm not sure how well creating
> > >>>>>
> > >>>>> the
> > >>>>>
> > >>>>> kstreamaggregates will go though because at that point I will
> > >>>>>
> > >>>>> have
> > >>>>>
> > >>>>> thrown
> > >>>>>
> > >>>>> away the type of the values. It will be type safe I just may
> > >>>>>
> > >>>>> need to
> > >>>>>
> > >>>>> do a
> > >>>>>
> > >>>>> little forcing.
> > >>>>>
> > >>>>> Thanks,
> > >>>>> Kyle
> > >>>>>
> > >>>>> On May 24, 2017 3:28 PM, "Guozhang Wang" <wangg...@gmail.com
> > >>>>>
> > >>>>> wrote:
> > >>>>>
> > >>>>> Kyle,
> > >>>>>
> > >>>>> Thanks for the explanations, my previous read on the wiki
> > >>>>>
> > >>>>> examples
> > >>>>>
> > >>>>> was
> > >>>>>
> > >>>>> wrong.
> > >>>>>
> > >>>>> So I guess my motivation should be "reduced" to: can we move
> > >>>>>
> > >>>>> the
> > >>>>>
> > >>>>> window
> > >>>>>
> > >>>>> specs param from "KGroupedStream#cogroup(..)" to
> > >>>>> "CogroupedKStream#aggregate(..)", and my motivations are:
> > >>>>>
> > >>>>> 1. minor: we can reduce the #.generics in CogroupedKStream
> > >>>>>
> > >>>>> from
> > >>>>>
> > >>>>> 3
> > >>>>>
> > >>>>> to
> > >>>>>
> > >>>>> 2.
> > >>>>>
> > >>>>> 2. major: this is for extensibility of the APIs, and since
> > >>>>>
> > >>>>> we
> > >>>>>
> > >>>>> are
> > >>>>>
> > >>>>> removing
> > >>>>>
> > >>>>> the "Evolving" annotations on Streams it may be harder to
> > >>>>>
> > >>>>> change it
> > >>>>>
> > >>>>> again
> > >>>>>
> > >>>>> in the future. The extended use cases are that people wanted
> > >>>>>
> > >>>>> to
> > >>>>>
> > >>>>> have
> > >>>>>
> > >>>>> windowed running aggregates on different granularities, e.g.
> > >>>>>
> > >>>>> "give
> > >>>>>
> > >>>>> me
> > >>>>>
> > >>>>> the
> > >>>>>
> > >>>>> counts per-minute, per-hour, per-day and per-week", and
> > >>>>>
> > >>>>> today
> > >>>>>
> > >>>>> in
> > >>>>>
> > >>>>> DSL
> > >>>>>
> > >>>>> we
> > >>>>>
> > >>>>> need to specify that case in multiple aggregate operators,
> > >>>>>
> > >>>>> which
> > >>>>>
> > >>>>> gets
> > >>>>>
> > >>>>> a
> > >>>>>
> > >>>>> state store / changelog, etc. And it is possible to optimize
> > >>>>>
> > >>>>> it
> > >>>>>
> > >>>>> as
> > >>>>>
> > >>>>> well
> > >>>>>
> > >>>>> to
> > >>>>>
> > >>>>> a single state store. Its implementation would be tricky as
> > >>>>>
> > >>>>> you
> > >>>>>
> > >>>>> need
> > >>>>>
> > >>>>> to
> > >>>>>
> > >>>>> contain different lengthed windows within your window store
> > >>>>>
> > >>>>> but
> > >>>>>
> > >>>>> just
> > >>>>>
> > >>>>> from
> > >>>>>
> > >>>>> the public API point of view, it could be specified as:
> > >>>>>
> > >>>>> CogroupedKStream stream = stream1.cogroup(stream2, ...
> > >>>>> "state-store-name");
> > >>>>>
> > >>>>> table1 = stream.aggregate(/*per-minute window*/)
> > >>>>> table2 = stream.aggregate(/*per-hour window*/)
> > >>>>> table3 = stream.aggregate(/*per-day window*/)
> > >>>>>
> > >>>>> while underlying we are only using a single store
> > >>>>>
> > >>>>> "state-store-name"
> > >>>>>
> > >>>>> for
> > >>>>>
> > >>>>> it.
> > >>>>>
> > >>>>>
> > >>>>> Although this feature is out of the scope of this KIP, I'd
> > >>>>>
> > >>>>> like
> > >>>>>
> > >>>>> to
> > >>>>>
> > >>>>> discuss
> > >>>>>
> > >>>>> if we can "leave the door open" to make such changes without
> > >>>>>
> > >>>>> modifying
> > >>>>>
> > >>>>> the
> > >>>>>
> > >>>>> public APIs .
> > >>>>>
> > >>>>> Guozhang
> > >>>>>
> > >>>>>
> > >>>>> On Wed, May 24, 2017 at 3:57 AM, Kyle Winkelman <
> > >>>>>
> > >>>>> winkelman.k...@gmail.com
> > >>>>>
> > >>>>> wrote:
> > >>>>>
> > >>>>>
> > >>>>> I allow defining a single window/sessionwindow one time
> > >>>>>
> > >>>>> when
> > >>>>>
> > >>>>> you
> > >>>>>
> > >>>>> make
> > >>>>>
> > >>>>> the
> > >>>>>
> > >>>>> cogroup call from a KGroupedStream. From then on you are
> > >>>>>
> > >>>>> using
> > >>>>>
> > >>>>> the
> > >>>>>
> > >>>>> cogroup
> > >>>>>
> > >>>>> call from with in CogroupedKStream which doesnt accept any
> > >>>>>
> > >>>>> additional
> > >>>>>
> > >>>>> windows/sessionwindows.
> > >>>>>
> > >>>>> Is this what you meant by your question or did I
> > >>>>>
> > >>>>> misunderstand?
> > >>>>>
> > >>>>> On May 23, 2017 9:33 PM, "Guozhang Wang" <
> > >>>>>
> > >>>>> wangg...@gmail.com
> > >>>>>
> > >>>>> wrote:
> > >>>>>
> > >>>>> Another question that came to me is on "window alignment":
> > >>>>>
> > >>>>> from
> > >>>>>
> > >>>>> the
> > >>>>>
> > >>>>> KIP
> > >>>>>
> > >>>>> it
> > >>>>>
> > >>>>> seems you are allowing users to specify a (potentially
> > >>>>>
> > >>>>> different)
> > >>>>>
> > >>>>> window
> > >>>>>
> > >>>>> spec in each co-grouped input stream. So if these window
> > >>>>>
> > >>>>> specs
> > >>>>>
> > >>>>> are
> > >>>>>
> > >>>>> different how should we "align" them with different input
> > >>>>>
> > >>>>> streams? I
> > >>>>>
> > >>>>> think
> > >>>>>
> > >>>>> it is more natural to only specify on window spec in the
> > >>>>>
> > >>>>> KTable<RK, V> CogroupedKStream#aggregate(Windows);
> > >>>>>
> > >>>>>
> > >>>>> And remove it from the cogroup() functions. WDYT?
> > >>>>>
> > >>>>>
> > >>>>> Guozhang
> > >>>>>
> > >>>>> On Tue, May 23, 2017 at 6:22 PM, Guozhang Wang <
> > >>>>>
> > >>>>> wangg...@gmail.com>
> > >>>>>
> > >>>>> wrote:
> > >>>>>
> > >>>>> Thanks for the proposal Kyle, this is a quite common use
> > >>>>>
> > >>>>> case
> > >>>>>
> > >>>>> to
> > >>>>>
> > >>>>> support
> > >>>>>
> > >>>>> such multi-way table join (i.e. N source tables with N
> > >>>>>
> > >>>>> aggregate
> > >>>>>
> > >>>>> func)
> > >>>>>
> > >>>>> with
> > >>>>>
> > >>>>> a single store and N+1 serdes, I have seen lots of people
> > >>>>>
> > >>>>> using
> > >>>>>
> > >>>>> the
> > >>>>>
> > >>>>> low-level PAPI to achieve this goal.
> > >>>>>
> > >>>>>
> > >>>>> On Fri, May 19, 2017 at 10:04 AM, Kyle Winkelman <
> > >>>>>
> > >>>>> winkelman.k...@gmail.com
> > >>>>>
> > >>>>> wrote:
> > >>>>>
> > >>>>> I like your point about not handling other cases such as
> > >>>>>
> > >>>>> count
> > >>>>>
> > >>>>> and
> > >>>>>
> > >>>>> reduce.
> > >>>>>
> > >>>>> I think that reduce may not make sense because reduce
> > >>>>>
> > >>>>> assumes
> > >>>>>
> > >>>>> that
> > >>>>>
> > >>>>> the
> > >>>>>
> > >>>>> input values are the same as the output values. With
> > >>>>>
> > >>>>> cogroup
> > >>>>>
> > >>>>> ...
> > >
> > > --
> > > Signature
> > > <http://www.openbet.com/> Michal Borowiecki
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--
-- Guozhang
