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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