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https://issues.apache.org/jira/browse/FLINK-3679?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15866919#comment-15866919
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ASF GitHub Bot commented on FLINK-3679:
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GitHub user haohui opened a pull request:
https://github.com/apache/flink/pull/3314
[FLINK-3679] DeserializationSchema should handle zero or more outputs
This PR adds a new interface, `RichKeyedDeserializationSchema`, to enable
the deserializer to produce zero or more outputs. The main use case is that
skipping corrupted messages in the Kafka stream.
Feedbacks (especially on backward compatibility) are highly appreciated.
You can merge this pull request into a Git repository by running:
$ git pull https://github.com/haohui/flink FLINK-3679
Alternatively you can review and apply these changes as the patch at:
https://github.com/apache/flink/pull/3314.patch
To close this pull request, make a commit to your master/trunk branch
with (at least) the following in the commit message:
This closes #3314
----
commit 7728acb3bc00a12a7552706be569710fbfdbd200
Author: Haohui Mai <[email protected]>
Date: 2017-02-14T22:19:29Z
[FLINK-3679] DeserializationSchema should handle zero or more outputs for
every input.
----
> DeserializationSchema should handle zero or more outputs for every input
> ------------------------------------------------------------------------
>
> Key: FLINK-3679
> URL: https://issues.apache.org/jira/browse/FLINK-3679
> Project: Flink
> Issue Type: Bug
> Components: DataStream API, Kafka Connector
> Reporter: Jamie Grier
> Assignee: Haohui Mai
>
> There are a couple of issues with the DeserializationSchema API that I think
> should be improved. This request has come to me via an existing Flink user.
> The main issue is simply that the API assumes that there is a one-to-one
> mapping between input and outputs. In reality there are scenarios where one
> input message (say from Kafka) might actually map to zero or more logical
> elements in the pipeline.
> Particularly important here is the case where you receive a message from a
> source (such as Kafka) and say the raw bytes don't deserialize properly.
> Right now the only recourse is to throw IOException and therefore fail the
> job.
> This is definitely not good since bad data is a reality and failing the job
> is not the right option. If the job fails we'll just end up replaying the
> bad data and the whole thing will start again.
> Instead in this case it would be best if the user could just return the empty
> set.
> The other case is where one input message should logically be multiple output
> messages. This case is probably less important since there are other ways to
> do this but in general it might be good to make the
> DeserializationSchema.deserialize() method return a collection rather than a
> single element.
> Maybe we need to support a DeserializationSchema variant that has semantics
> more like that of FlatMap.
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