Andrey Zagrebin created FLINK-10374:
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Summary: [Map State] Let user value serializer handle null values
Key: FLINK-10374
URL: https://issues.apache.org/jira/browse/FLINK-10374
Project: Flink
Issue Type: Improvement
Components: State Backends, Checkpointing
Reporter: Andrey Zagrebin
Fix For: 2.0.0
Prior to Flink 2.0, value serializer in map state does not rely on user
serializer to handle null value. Map serializer always prepends the serialized
value with one byte boolean flag which signals whether it is null or not.
Map state state supports storing null user values for the following
get/contains semantics:
remove(k); contains(k) -> false; put(k, null); get(k) -> null; contains(k) ->
true;
It means that if user does not need this semantics and storing null values or
the user value serializer already supports null values, one byte will be always
wasted in the serialized value.
Rather than to hardcode null handling in map state serializer, it can be
optional and up to the user decide the behaviour. If users want to add null
support for their serializer, they could wrap it e.g. with NullableSerializer
which can do the same prepending with null flag.
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