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

[Shang Yuanchun (Jira)]

aitozi created FLINK-10343:
------------------------------

             Summary: 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
             Fix For: 1.7.0


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

```
snapshot() {
 for(Map.Entry<String, String> entry : map.entrySet()){
     setCurrentKey(entry.getKey());
     valueState.update(entry.getValue()); // put value back to state backend
}}
```
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 [~[hidden email]] [~azagrebin] ?




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