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From Ryan Blue <rb...@netflix.com.INVALID>
Subject Re: [DISCUSS] Disable streaming query with possible correctness issue by default
Date Tue, 10 Nov 2020 23:47:59 GMT
+1, I agree with Tom.

On Tue, Nov 10, 2020 at 3:00 PM Dongjoon Hyun <dongjoon.hyun@gmail.com>
wrote:

> +1 for Apache Spark 3.1.0.
>
> Bests,
> Dongjoon.
>
> On Tue, Nov 10, 2020 at 6:17 AM Tom Graves <tgraves_cs@yahoo.com.invalid>
> wrote:
>
>> +1 since its a correctness issue, I think its ok to change the behavior
>> to make sure the user is aware of it and let them decide.
>>
>> Tom
>>
>> On Saturday, November 7, 2020, 01:00:11 AM CST, Liang-Chi Hsieh <
>> viirya@gmail.com> wrote:
>>
>>
>> Hi devs,
>>
>> In Spark structured streaming, chained stateful operators possibly
>> produces
>> incorrect results under the global watermark. SPARK-33259
>> (https://issues.apache.org/jira/browse/SPARK-33259) has an example
>> demostrating what the correctness issue could be.
>>
>> Currently we don't prevent users running such queries. Because the
>> possible
>> correctness in chained stateful operators in streaming query is not
>> straightforward for users. From users perspective, it will possibly be
>> considered as a Spark bug like SPARK-33259. It is also possible the worse
>> case, users are not aware of the correctness issue and use wrong results.
>>
>> IMO, it is better to disable such queries and let users choose to run the
>> query if they understand there is such risk, instead of implicitly running
>> the query and let users to find out correctness issue by themselves.
>>
>> I would like to propose to disable the streaming query with possible
>> correctness issue in chained stateful operators. The behavior can be
>> controlled by a SQL config, so if users understand the risk and still want
>> to run the query, they can disable the check.
>>
>> In the PR (https://github.com/apache/spark/pull/30210), the concern I got
>> for now is, this changes current behavior and by default it will break
>> some
>> existing streaming queries. But I think it is pretty easy to disable the
>> check with the new config. In the PR currently there is no objection but
>> suggestion to hear more voices. Please let me know if you have some
>> thoughts.
>>
>> Thanks.
>> Liang-Chi Hsieh
>>
>>
>>
>> --
>> Sent from: http://apache-spark-developers-list.1001551.n3.nabble.com/
>>
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>>
>>

-- 
Ryan Blue
Software Engineer
Netflix

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