Tzu-Li (Gordon) Tai created FLINK-9808:
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Summary: Implement state conversion procedure in state backends
Key: FLINK-9808
URL: https://issues.apache.org/jira/browse/FLINK-9808
Project: Flink
Issue Type: Sub-task
Components: State Backends, Checkpointing
Reporter: Tzu-Li (Gordon) Tai
Assignee: Aljoscha Krettek
Fix For: 1.6.0
With FLINK-9377 in place and that config snapshots serve as the single source
of truth for recreating restore serializers, the next step would be to utilize
this when performing a full-pass state conversion (i.e., read with old /
restore serializer, write with new serializer).
For Flink's heap-based backends, it can be seen that state conversion
inherently happens, since all state is always deserialized after restore with
the restore serializer, and written with the new serializer on snapshots.
For the RocksDB state backend, since state is lazily deserialized, state
conversion needs to happen for per-registered state on their first access if
the registered new serializer has a different serialization schema than the
previous serializer.
This task should consist of three parts:
1. Allow {{CompatibilityResult}} to correctly distinguish between whether the
new serializer's schema is a) compatible with the serializer as it is, b)
compatible after the serializer has been reconfigured, or c) incompatible.
2. Introduce state conversion procedures in the RocksDB state backend. This
should occur on the first state access.
3. Make sure that all other backends no longer do redundant serializer
compatibility checks. That is not required because those backends always
perform full-pass state conversions.
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