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https://issues.apache.org/jira/browse/FLINK-23143?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17534026#comment-17534026
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Roman Khachatryan commented on FLINK-23143:
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Thanks a lot for sharing the prototype.
I like the simplicity of your solution, but I think the concern I expressed
above (about creation of multiple state objects) is valid.
Besides that, RegisteredKeyValueStateBackendMetaInfo seems implementation
detail of a state backend, so it shouldn't be exposed.
Regarding the key serializer upgrade, I think it's [not
supported|https://nightlies.apache.org/flink/flink-docs-master/docs/dev/datastream/fault-tolerance/serialization/schema_evolution/]
currently and therefore is out of the scope of this ticket.
> 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
> Labels: pull-request-available
> 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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