Xiaogang Shi created FLINK-5024:
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Summary: Add SimpleStateDescriptor to clarify the concepts
Key: FLINK-5024
URL: https://issues.apache.org/jira/browse/FLINK-5024
Project: Flink
Issue Type: Improvement
Reporter: Xiaogang Shi
Currently, StateDescriptors accept two type arguments : the first one is the
type of the created state and the second one is the type of the values in the
states.
The concepts however is a little confusing here because in ListStates, the
arguments passed to the StateDescriptors are the types of the list elements
instead of the lists. It also makes the implementation of MapStates difficult.
I suggest not to put the type serializer in StateDescriptors, making
StateDescriptors independent of the data structures of the values.
A new type of StateDescriptor named SimpleStateDescriptor can be provided to
abstract those states (namely ValueState, ReducingState and FoldingState) whose
states are not composited.
The states (e.g. ListStates and MapStates) can implement their own descriptors
according to their data structures.
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