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https://issues.apache.org/jira/browse/FLINK-23143?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17525953#comment-17525953
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Roman Khachatryan commented on FLINK-23143:
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Hi, [~masteryhx] .
I meant an approach similar to
[FunctionDelegationHelper|https://github.com/apache/flink/blob/cc6d1a27bafe38e76d6f9f0d480fdcb7e017be3a/flink-state-backends/flink-statebackend-changelog/src/main/java/org/apache/flink/state/changelog/restore/FunctionDelegationHelper.java]
from ChangelogKeyedStateBackend. But instead of function, it would hold and
update the Serializer. No state (like ValueState) should be added. It's already
used in FLINK-23252 IIUC.
I didn't fully understood your proposal, could you share your POC?
> Support state migration
> -----------------------
>
> Key: FLINK-23143
> URL: https://issues.apache.org/jira/browse/FLINK-23143
> Project: Flink
> Issue Type: Sub-task
> Components: Runtime / State Backends
> Reporter: Roman Khachatryan
> Priority: Minor
> Fix For: 1.16.0
>
>
> ChangelogKeyedStateBackend.getOrCreateKeyedState is currently used during
> recovery; on 1st user access, it doesn't update metadata nor migrate state
> (as opposed to other backends).
>
> The proposed solution is to
> # wrap serializers (and maybe other objects) in getOrCreateKeyedState
> # store wrapping objects in a new map keyed by state name
> # pass wrapped objects to delegatedBackend.createInternalState
> # on 1st user access, lookup wrapper and upgrade its wrapped serializer
> This should be done for both KV/PQ states.
>
> See also [https://github.com/apache/flink/pull/15420#discussion_r656934791]
>
> cc: [~yunta]
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