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From "Xiaogang Shi (JIRA)" <j...@apache.org>
Subject [jira] [Created] (FLINK-5024) Add SimpleStateDescriptor to clarify the concepts
Date Mon, 07 Nov 2016 02:24:59 GMT
Xiaogang Shi created FLINK-5024:

             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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