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Date: Fri, 15 Jan 2016 10:24:39 +0000 (UTC)
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Subject: [jira] [Commented] (FLINK-1870) Reintroduce Indexed reader
 functionality to streaming
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    [ https://issues.apache.org/jira/browse/FLINK-1870?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15101584#comment-15101584 ] 

ASF GitHub Bot commented on FLINK-1870:
---------------------------------------

Github user aljoscha commented on the pull request:

    https://github.com/apache/flink/pull/1483#issuecomment-171926900
  
    Hi,
    I would be strongly against exposing the input channel index in any way to operators/user functions. How the index of a channel maps to an upstream operator is internal to the network layer and dependent on several things, some of which are not even deterministic IMHO. Off the top of my head it should depend on the number of upstream tasks, the parallelism of these upstream tasks and the order in which the system choses to attach the channels.
    
    I think your goal can be achieved by adding a task-id field in the message wrapper and setting this when emitting elements. Setting this for every processed element (if using the Storm combat layer or not) seems quite wasteful to me.


> Reintroduce Indexed reader functionality to streaming
> -----------------------------------------------------
>
>                 Key: FLINK-1870
>                 URL: https://issues.apache.org/jira/browse/FLINK-1870
>             Project: Flink
>          Issue Type: Task
>          Components: Streaming
>            Reporter: Gyula Fora
>            Assignee: Matthias J. Sax
>            Priority: Minor
>
> The Indexed record reader classes (IndexedReaderIterator, IndexedMutableReader) were introduced to allow the streaming operators to access the index of the last read channel from the input gate. This was a necessary step toward future input sorting operators.
> Unfortunately this untested feature was patched away by the following commit:
> https://github.com/apache/flink/commit/5232c56b13b7e13e2cf10dbe818c221f5557426d
> At some point we need to reimplement these features with proper tests.


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