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From Fabian Hueske <fhue...@gmail.com>
Subject Re: [DISCUSS]: Integrating Flink Table API & SQL with CEP
Date Wed, 07 Jun 2017 13:40:03 GMT
Thanks Dian and Jark for this proposal!

As you wrote, Till and I (and Kostas) have been thinking about this for
some time but haven't had time to work on this feature.
I think it would be a great addition and value add for Flink's SQL support
and Table API.

I read the proposal and think it is very good. We might need to add a bit
more details, esp. when planning the concrete steps of the implementation.

A few comments to the proposal:
- IMO, the development should start focusing on SQL and its semantics.
Pattern support for the Table API should be added later. We followed that
approach for the OVER windows and I think it worked quiet well.
- We probably want to reuse as much as possible from the CEP library. That
means we need to check if the semantics of the CEP library and Oracle's
PATTERN syntax are aligned (or how we can express the PATTERN semantics
with the CEP library). This should be one of the first steps, IMO.
- I would make the orderBy() clause required. In regular SQL rows have no
order, so we need to make that explicit (this would also be consistent with
the OVER windows).

Let me know what you think.

Best, Fabian

2017-06-07 11:41 GMT+02:00 Kostas Kloudas <k.kloudas@data-artisans.com>:

> Thanks a lot for opening the discussion!
>
> This is a really interesting idea that has been in our heads
> since the first implementation of the CEP library.
>
> A big +1 for moving forward with this.
>
> And as for the design document, I will definitely have a look
> and comment there.
>
> Kostas
>
> On Jun 7, 2017, at 10:05 AM, Jark Wu <jark@apache.org> wrote:
>
> Sorry, I forgot to cc you guys @Fabian, @Timo, @Till, @Kostas
>
> 2017-06-07 15:42 GMT+08:00 Jark Wu <jark@apache.org>:
>
>> Hi devs,
>>
>> Dian and me and our teammates have investigated this for a long time. We
>> think consolidating Flink SQL and CEP is an exciting thing for Flink. It'll
>> make SQL more powerful and give users the ability to easily and quickly
>> build CEP applications.  And I find Flink community has also talked about
>> this idea before, such as the mailing list [1] and [2] and Fabian & Till's
>> talk in Flink Forward 2016 [3].
>>
>> I think THIS IS THE POINT to bring up this topic again. Because we
>> already have pattern matching foundation in Flink CEP library, and Stream
>> SQL is ready now and Calcite has partially supported pattern matching
>> syntax!  We also drafted a design doc about how to integrate SQL and CEP,
>> and how to support CEP on Table API. https://docs.google.com/docume
>> nt/d/1HaaO5eYI1VZjyhtVPZOi3jVzikU7iK15H0YbniTnN30/edit?usp=sharing
>>
>>
>> @Fabian, @Timo, @Till, @Kostas I include you into this discussion, it
>> would be great to hear your response.
>>
>>
>> What do others think?
>>
>>
>> [1] http://apache-flink-mailing-list-archive.1008284.n3.nabble.
>> com/Add-CEP-library-to-Flink-td9743.html#a9787
>>
>> [2] http://apache-flink-mailing-list-archive.1008284.n3.nabble.
>> com/Effort-to-add-SQL-StreamSQL-to-Flink-td9727.html#a9790
>>
>> [3] https://www.slideshare.net/tillrohrmann/streaming-analytics-
>> cep-two-sides-of-the-same-coin
>>
>>
>> Regards,
>>
>> Jark Wu
>>
>>
>>
>> 2017-06-07 13:50 GMT+08:00 Dian Fu <dianfu@apache.org>:
>>
>>> Hi everyone,
>>>
>>> Flink's CEP library is a great library for complex event processing, more
>>> and more customers are expressing their interests in it. But it also has
>>> some limitations that users usually have to write a lot of code even for
>>> a
>>> very simple pattern match use case as it currently only supports the Java
>>> API.
>>> We have investigated some popular CEP products such as esper [1] and
>>> siddhi
>>> [2] and found that most of these CEP products support SQL-like
>>> expressions
>>> such as EPL to describe the match pattern. But these solutions also have
>>> the drawbacks that the pattern match languages are not standard SQL, the
>>> learn curve is steep for users and it's impossible to integrate them into
>>> the Flink Table API & SQL.
>>> We find that Oracle's CEP solution CQL [3] supports a new pattern
>>> recognition clause match_recognize which is a pattern recognition clause
>>> proposed in this paper [4]. It proposes a set of new syntaxes to define
>>> match pattern in sql expression. Calcite already supports part of this
>>> standard [5].  I think it will be of great value to support expressing
>>> pattern recognition clause with match_recognize clause by integrating it
>>> with Flink Table API & SQL and the Flink CEP library. Any thoughts?
>>>
>>> [1] http://www.espertech.com
>>> [2] https://github.com/wso2/siddhi
>>> [3]
>>> https://docs.oracle.com/middleware/1213/eventprocessing/cql-
>>> reference/GUID-34D4968E-C55A-4BC7-B1CE-C84B202217BD.htm#CQLLR1531
>>> [4]
>>> http://web.cs.ucla.edu/classes/winter17/cs240B/notes/row-pat
>>> tern-recogniton-11.pdf
>>> [5] https://issues.apache.org/jira/browse/CALCITE-1570
>>>
>>> Best Regards,
>>> Dian
>>>
>>
>>
>
>

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