[jira] [Commented] (FLINK-10343) Expose setCurrentKey method to streamRuntimeContext

["Kostas Kloudas (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/FLINK-10343?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16691409#comment-16691409 ] 

Kostas Kloudas commented on FLINK-10343:
----------------------------------------

Given that we all agreed that this functionality requires a custom state backend rather than simply exposing the {{setCurrentKey}}, I would suggest to close this issue and open new ones as soon as we have a plan for how to implement this state backend. 

I will leave the issue open for another 2 days so that anyone can express his/her objection (if any) and then close it.

> Expose setCurrentKey method to streamRuntimeContext
> ---------------------------------------------------
>
>                 Key: FLINK-10343
>                 URL: https://issues.apache.org/jira/browse/FLINK-10343
>             Project: Flink
>          Issue Type: Improvement
>          Components: Streaming
>    Affects Versions: 1.7.0
>            Reporter: aitozi
>            Assignee: aitozi
>            Priority: Major
>             Fix For: 1.8.0
>
>
> when we use reducing state / aggregating keyed state and so on , we have to read value from state backend and update the value with userFunction and then put back to state backend. If we can just cache certain data in heap with a map, and update once in snapshot method with 
> {code:java}
> snapshot() {
>  for(Map.Entry<String, String> entry : map.entrySet()){
>      setCurrentKey(entry.getKey());
>      valueState.update(entry.getValue()); // put value back to state backend
> }}
> {code}
> we just have to expose the setCurrentKey to userFunction and the will enable the ability to cache partitial keyedState in memory by userself.
> what's your opinion [~stefanrichter83@gmail.com] [~azagrebin] ? 



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