[GitHub] flink issue #2367: [FLINK-3703][cep] Add sequence matching semantics to disc...

[tillrohrmann <gi...@git.apache.org>]

Github user tillrohrmann commented on the issue:

    https://github.com/apache/flink/pull/2367
  
    Thanks for your contribution and apologies for the late review @mushketyk. I think your implementation goes into the right direction and I really like the testing.
    
    I think what we still can and should improve is to pull out the `MatchingBehaviour` out of the `SharedBuffer` and the `State`. The `NFA` should be the only component which is responsible for the matching behaviour. I think we can achieve this if we pimp the `SharedBuffer` a little bit.
    
    So what should roughly happen is that the `NFA` removes computation states which are not longer valid. Furthermore, we have to clean up the `SharedBuffer` and remove `SharedBufferEntries` which depend on other `SharedBufferEntries` which are no longer valid (e.g. due to `MatchingBehaviour.afterLast`). 
    
    So when you have a `SharedBufferEntry` representing a certain state which is part of the currently matched sequence and `MatchingBehaviour.afterLast`, then you have to find out all `SharedBufferEntries` which depend on this state (children) and remove them. That you have to do until you reach the youngest descendant. Currently we can only find the predecessors for a given `SharedBufferEntry` but not the children. I think that would have to be added in order to implement the different `MatchingBehaviours`.


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