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From Jungtaek Lim <kabhwan.opensou...@gmail.com>
Subject Re: What's the root cause of not supporting multiple aggregations in structured streaming?
Date Sat, 26 Sep 2020 02:30:56 GMT
Thanks Etienne! Yeah I forgot to say nice talking with you again. And sorry
I forgot to send the reply (was in draft).

Regarding investment in SS, well, unfortunately I don't know - I'm just an
individual. There might be various reasons to do so, most probably
"priority" among the stuff. There's not much I could change.

I agree the workaround is sub-optimal, but unless I see sufficient support
in the community I probably couldn't make it go forward. I'll just say
there's an elephant in the room - as the project goes forward for more than
10 years, backward compatibility is a top priority concern in the project,
even across the major versions along the features/APIs. It is great for end
users to migrate the version easily, but also blocks devs to fix the bad
design once it ships. I'm the one complaining about these issues in the dev
list, and I don't see willingness to correct them.


On Fri, Sep 4, 2020 at 5:55 PM Etienne Chauchot <echauchot@apache.org>
wrote:

> Hi Jungtaek Lim,
>
> Nice to hear from you again since last time we talked :) and congrats on
> becoming a Spark committer in the meantime ! (if I'm not mistaking you were
> not at the time)
>
> I totally agree with what you're saying on merging structural parts of
> Spark without having a broader consensus. What I don't understand is why
> there is not more investment in SS. Especially because in another thread
> the community is discussing about deprecating the regular DStream streaming
> framework.
>
> Is the orientation of Spark now mostly batch ?
>
> PS: yeah I saw your update on the doc when I took a look at 3.0 preview 2
> searching for this particular feature. And regarding the workaround, I'm
> not sure it meets my needs as it will add delays and also may mess up with
> watermarks.
>
> Best
>
> Etienne Chauchot
>
>
> On 04/09/2020 08:06, Jungtaek Lim wrote:
>
> Unfortunately I don't see enough active committers working on Structured
> Streaming; I don't expect major features/improvements can be brought in
> this situation.
>
> Technically I can review and merge the PR on major improvements in SS, but
> that depends on how huge the proposal is changing. If the proposal brings
> conceptual change, being reviewed by a committer wouldn't still be enough.
>
> So that's not due to the fact we think it's worthless. (That might be only
> me though.) I'd understand as there's not much investment on SS. There's
> also a known workaround for multiple aggregations (I've documented in the
> SS guide doc, in "Limitation of global watermark" section), though I
> totally agree the workaround is bad.
>
> On Tue, Sep 1, 2020 at 12:28 AM Etienne Chauchot <echauchot@apache.org>
> wrote:
>
>> Hi all,
>>
>> I'm also very interested in this feature but the PR is open since January
>> 2019 and was not updated. It raised a design discussion around watermarks
>> and a design doc was written (
>> https://docs.google.com/document/d/1IAH9UQJPUiUCLd7H6dazRK2k1szDX38SnM6GVNZYvUo/edit#heading=h.npkueh4bbkz1).
>> We also commented this design but no matter what it seems that the subject
>> is still stale.
>>
>> Is there any interest in the community in delivering this feature or is
>> it considered worthless ? If the latter, can you explain why ?
>>
>> Best
>>
>> Etienne
>> On 22/05/2019 03:38, 张万新 wrote:
>>
>> Thanks, I'll check it out.
>>
>> Arun Mahadevan <arunm@apache.org> 于 2019年5月21日周二 01:31写道:
>>
>>> Heres the proposal for supporting it in "append" mode -
>>> https://github.com/apache/spark/pull/23576. You could see if it
>>> addresses your requirement and post your feedback in the PR.
>>> For "update" mode its going to be much harder to support this without
>>> first adding support for "retractions", otherwise we would end up with
>>> wrong results.
>>>
>>> - Arun
>>>
>>>
>>> On Mon, 20 May 2019 at 01:34, Gabor Somogyi <gabor.g.somogyi@gmail.com>
>>> wrote:
>>>
>>>> There is PR for this but not yet merged.
>>>>
>>>> On Mon, May 20, 2019 at 10:13 AM 张万新 <kevinzwx1992@gmail.com>
wrote:
>>>>
>>>>> Hi there,
>>>>>
>>>>> I'd like to know what's the root reason why multiple aggregations on
>>>>> streaming dataframe is not allowed since it's a very useful feature,
and
>>>>> flink has supported it for a long time.
>>>>>
>>>>> Thanks.
>>>>>
>>>>

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