Roman Grebennikov created FLINK-18631:
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Summary: Serializer for scala sealed trait hierarchies
Key: FLINK-18631
URL:
https://issues.apache.org/jira/browse/FLINK-18631 Project: Flink
Issue Type: Improvement
Components: API / Type Serialization System
Affects Versions: 1.11.0
Reporter: Roman Grebennikov
Currently, when flink serialization system spots an ADT-style class hierarchy in the Scala code, it falls back to GenericType and kryo serialization, which may introduce performance issues. For example, for code:
{{sealed trait ADT}}{{case class Foo(a: String) extends ADT}}{{case class Bar(b: Int) extends ADT}}{{env.fromCollection(List[ADT](Foo("a"),Bar(1))).collect()}}
It will fall back to Kryo even if there is no problem with dealing with List[Foo] or List[Bar] separately. Using ADTs is a convenient way in Scala to model different types of messages, but Flink type system performance limits it to only a non performance-critical paths.
It would be nice to have a sealed trait hierarchies support out of the box without kryo fallback.
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