Weiqing Yang created FLINK-40296:
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Summary: Add an object-level migrate hook to TypeSerializerSnapshot
Key: FLINK-40296
URL: https://issues.apache.org/jira/browse/FLINK-40296
Project: Flink
Issue Type: Sub-task
Components: API / Type Serialization System
Reporter: Weiqing Yang
FLIP-527 needs a way for a serializer snapshot to transform an
already-deserialized state value from the schema it was written with into the
schema the current serializer expects.
This adds a single default method to TypeSerializerSnapshot:
{code:java}
default T migrate(TypeSerializerSnapshot<T> oldSerializerSnapshot, T value) {
return value;
}
{code}
Like resolveSchemaCompatibility, it is invoked on the new snapshot and
receives the old snapshot as its argument. The default returns the value
unchanged, so behavior is unaffected for
every existing serializer: a value deserialized with the prior serializer is
structurally compatible with the current one and can be re-serialized as is.
Serializers whose in-memory representation is coupled to the schema override
it. The RowData serializer does so in a follow-up subtask, remapping fields by
name.
FLIP-527:
https://cwiki.apache.org/confluence/spaces/FLINK/pages/353601981/FLIP-527+State+Schema+Evolution+for+RowData
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