Liu created FLINK-39375:
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Summary: Add explicit serialVersionUID to WatermarkAlignmentParams
Key: FLINK-39375
URL: https://issues.apache.org/jira/browse/FLINK-39375
Project: Flink
Issue Type: Improvement
Reporter: Liu
{{WatermarkAlignmentParams}} implements {{Serializable}} but does not declare
an explicit {{{}serialVersionUID{}}}.
Without an explicit {{{}serialVersionUID{}}}, the JVM auto-generates one based
on the class structure (fields, methods, etc.). If the class is modified in a
future release — even with a minor, non-breaking change — the auto-generated
UID will change, causing {{InvalidClassException}} during deserialization.
This is particularly problematic in Flink because {{WatermarkAlignmentParams}}
may be serialized as part of job graphs and checkpoints/savepoints. A changed
UID would prevent users from restoring savepoints taken on a prior version
after upgrading Flink, breaking savepoint compatibility.
Additionally, the class is annotated with {{{}@PublicEvolving{}}}, which means
it is part of Flink's public API and should maintain backward compatibility.
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