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https://issues.apache.org/jira/browse/FLINK-6849?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16045459#comment-16045459
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mingleizhang commented on FLINK-6849:
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Yep. [~srichter]. We should have a concrete plan refactor operator state
backend before we start do it. About more implementations for that, I think we
could choose RocksDB as it's concrete implementations for it as well and
extends an abstract base class that we called {{AbstractOperatorStateBackend}}.
And we can also caches registered state in this abstract base class. BTW, If
we use RocksDB as its implementations, we can have a large state for a job. As
for the other way to achieve operator state backend, I have no idea about it at
the moment. [~tzulitai] What do you think ?
> 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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