Kostas Kloudas created FLINK-5932:
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Summary: Order of legacy vs new state initialization in the
AbstractStreamOperator.
Key: FLINK-5932
URL: https://issues.apache.org/jira/browse/FLINK-5932
Project: Flink
Issue Type: Bug
Components: DataStream API
Affects Versions: 1.2.0
Reporter: Kostas Kloudas
Fix For: 1.3.0
Currently in the `AbstractStreamOperator::initializeState(OperatorStateHandles
stateHandles)`, the `restoreStreamCheckpointed` which is responsible for
restoring state from previous Flink versions, (backwards compatibility) is
called before the `initializeState(StateInitializationContext context)` which
is responsible for initializing the state in Flink 1.2.
This has the negative side effect that when implementing the backwards
compatibility strategy for a given operator, we have to restore the old state,
store it in local variables, and register it with the new state abstractions in
the `initializeState()` or the `open()`. This creates a lot of unnecessary code
in the operators, and potential memory leaks if the local variables are not
"null-ified".
This issue proposes to call the `restoreStreamCheckpointed` after the
`initializeState(StateInitializationContext context)`. This way, the new
operator state will have been initialized (e.g. keyed state), and the
`restoreStreamCheckpointed` will be able to register its state directly with
the new abstractions, instead of putting it in local variables and wait for the
`initializeState` or the `open()` to re-register it.
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