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From dianfu <...@git.apache.org>
Subject [GitHub] flink pull request #4331: [FLINK-7169][CEP] Support AFTER MATCH SKIP functio...
Date Mon, 31 Jul 2017 03:41:02 GMT
Github user dianfu commented on a diff in the pull request:

    https://github.com/apache/flink/pull/4331#discussion_r130266394
  
    --- Diff: flink-libraries/flink-cep/src/main/java/org/apache/flink/cep/nfa/NFA.java ---
    @@ -551,18 +579,47 @@ private boolean isSelfIgnore(final StateTransition<T> edge)
{
     								nextVersion,
     								startTimestamp);
     					}
    +
    +					switch (skipStrategy.getStrategy()) {
    +						case SKIP_PAST_LAST_EVENT:
    +							if (nextState.isFinal()) {
    +								resultingComputationStates.add(createStartComputationState(computationState,
event));
    +							}
    +							break;
    +						case SKIP_TO_FIRST:
    +							if (nextState.getName().equals(skipStrategy.getPatternName()) &&
    +								!nextState.getName().equals(currentState.getName())) {
    +								ComputationState<T> startComputationState = createStartComputationState(computationState,
event);
    +								if (callLevel > 0) {
    +									throw new RuntimeException("infinite loop! Will abort the match process, please
rewrite your pattern query");
    +								}
    +								// feed current matched event to the state.
    +								Collection<ComputationState<T>> computationStates = computeNextStates(startComputationState,
event, timestamp, callLevel++);
    +								resultingComputationStates.addAll(computationStates);
    +							} else if (previousState == null && currentState.getName().equals(skipStrategy.getPatternName()))
{
    +								throw new RuntimeException("infinite loop! Will abort the match process, please
rewrite your pattern query");
    +							}
    +							break;
    +						case SKIP_TO_LAST:
    +							if (currentState.getName().equals(skipStrategy.getPatternName()) &&
    +								!nextState.getName().equals(currentState.getName())) {
    +								ComputationState<T> startComputationState = createStartComputationState(computationState,
event);
    +								if (callLevel > 0) {
    +									throw new RuntimeException("infinite loop! Will abort the match process, please
rewrite your pattern query");
    +								}
    +								// feed current matched event to the state.
    +								Collection<ComputationState<T>> computationStates = computeNextStates(startComputationState,
event, timestamp, callLevel++);
    +								resultingComputationStates.addAll(computationStates);
    +							}
    +							break;
    +					}
     					break;
     			}
     		}
     
    -		if (computationState.isStartState()) {
    -			int totalBranches = calculateIncreasingSelfState(
    -					outgoingEdges.getTotalIgnoreBranches(),
    -					outgoingEdges.getTotalTakeBranches());
    -
    -			DeweyNumber startVersion = computationState.getVersion().increase(totalBranches);
    -			ComputationState<T> startState = ComputationState.createStartState(this, computationState.getState(),
startVersion);
    -			resultingComputationStates.add(startState);
    +		if (computationState.isStartState() &&
    +			skipStrategy.getStrategy() == AfterMatchSkipStrategy.SkipStrategy.SKIP_TO_NEXT_EVENT)
{
    --- End diff --
    
    If the skip strategy is  @**SKIP_PAST_LAST_EVENT**, for pattern **a nextby b** and inputs
**a1 c a2 b2**, the output should be **a2 b2**, but per the current implementation, I'm afraid
there will be no output as after **a1** is processed, the start ComputationState will be consumed,
but there is no chance to add the start ComputationState later and so **a2 b2** can not be
matched. Right? For other skip strategy, I'm afraid there may be also such issues.


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