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1. The following (~20) classes to be refactored to allow extension (extracting methods, adding hooks, etc.):
1. (Heap-) KeyedStateBackend, SnapshotStrategy, RestoreOperation
2. (CopyOnWrite-) Map, Entry, State, Snapshots
3. RegisteredKeyValueStateBackendMetaInfo
2. Incremental versions of the following (~10) classes to be added:
1. HashMapStateBackend
2. CoW StateMap, StateMapSnapshot, StateTable, StateTableSnapshot
3. StateMapEntry
4. KeyedStateBackend, RestoreOperation, SnapshotStrategy,
5. RegisteredKeyValueStateBackendMetaInfo
6. StateSnapshotRestore
3. The following new classes to be added (~10):
1. RemovalLog
2. For each state type: Diff, DiffSerializer, Journal, JournalFactory
3. StateSnapshotKeyGroupReaderV7
4. The following classes to be updated:
1. StateTableByKeyGroupReaders: add new version
2. Fs- and MemoryStateBackend will have additional settings to construct incremental backend versions

The backend/new classes will reside in a new module under flink/flink-state-backends.

Public Interfaces

Code: see Proposed changes

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