[jira] [Created] (FLINK-6849) Refactor operator state backend and internal operator state hierarchy

["Tzu-Li (Gordon) Tai (JIRA)" <ji...@apache.org>]

Tzu-Li (Gordon) Tai created FLINK-6849:
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             Summary: Refactor operator state backend and internal operator state hierarchy
                 Key: FLINK-6849
                 URL: https://issues.apache.org/jira/browse/FLINK-6849
             Project: Flink
          Issue Type: Improvement
          Components: State Backends, Checkpointing
            Reporter: Tzu-Li (Gordon) Tai


Currently, compared to the keyed state backends, the operator state backends, as well as operator state interfaces, lacks proper hierarchy.

One issue with this lack of hierarchy is that the general concerns of implementing state registration is different between the keyed and operator backends (aside from what is naturally different, such as namespace and key which is not relevant for the operator backend). For example, in the keyed backend hierarchy, {{AbstractKeyedStateBackend}} has caches that shortcuts re-accessing already registered state. This behaviour is missing in the operator backend hierarchy, and for example needs to be explicitly handled by the concrete {{DefaultOperatorStateBackend}} subclass implementation.

As of now, the need of a proper hierarchy also on the operator backend side might not be that prominent, but will mostly likely become more prominent  as we wish to introduce more state structures for operator state (e.g. a {{MapState}} for operator state has already been discussed a few times already) as well as more options besides memory-backed operator state.



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