Github user kl0u commented on a diff in the pull request: https://github.com/apache/flink/pull/3477#discussion_r106107521 --- Diff: flink-libraries/flink-cep/src/main/java/org/apache/flink/cep/nfa/compiler/NFACompiler.java --- @@ -74,88 +76,233 @@ */ @SuppressWarnings("unchecked") public static <T> NFAFactory<T> compileFactory( - Pattern<T, ?> pattern, - TypeSerializer<T> inputTypeSerializer, + final Pattern<T, ?> pattern, + final TypeSerializer<T> inputTypeSerializer, boolean timeoutHandling) { if (pattern == null) { // return a factory for empty NFAs - return new NFAFactoryImpl<T>(inputTypeSerializer, 0, Collections.<State<T>>emptyList(), timeoutHandling); + return new NFAFactoryImpl<>(inputTypeSerializer, 0, Collections.<State<T>>emptyList(), timeoutHandling); } else { - // set of all generated states - Map<String, State<T>> states = new HashMap<>(); - long windowTime; + final NFAFactoryCompiler<T> nfaFactoryCompiler = new NFAFactoryCompiler<>(pattern); + nfaFactoryCompiler.compileFactory(); + return new NFAFactoryImpl<>(inputTypeSerializer, nfaFactoryCompiler.getWindowTime(), nfaFactoryCompiler.getStates(), timeoutHandling); + } + } - // this is used to enforse pattern name uniqueness. - Set<String> patternNames = new HashSet<>(); + private static class NFAFactoryCompiler<T> { - Pattern<T, ?> succeedingPattern; - State<T> succeedingState; - Pattern<T, ?> currentPattern = pattern; + private final Set<String> usedNames = new HashSet<>(); + private final List<State<T>> states = new ArrayList<>(); + private long windowTime = 0; + private Pattern<T, ?> currentPattern; + + NFAFactoryCompiler(final Pattern<T, ?> pattern) { + this.currentPattern = pattern; + } + + /** + * Compiles the given pattern into a {@link NFAFactory}. The NFA factory can be used to create + * multiple NFAs. + */ + void compileFactory() { // we're traversing the pattern from the end to the beginning --> the first state is the final state - State<T> currentState = new State<>(currentPattern.getName(), State.StateType.Final); - patternNames.add(currentPattern.getName()); + State<T> sinkState = createEndingState(); + // add all the normal states + sinkState = createMiddleStates(sinkState); + // add the beginning state + createStartState(sinkState); + } + + List<State<T>> getStates() { + return states; + } - states.put(currentPattern.getName(), currentState); + long getWindowTime() { + return windowTime; + } + + private State<T> createEndingState() { + State<T> sinkState = new State<>(ENDING_STATE_NAME, State.StateType.Final); + states.add(sinkState); + usedNames.add(ENDING_STATE_NAME); windowTime = currentPattern.getWindowTime() != null ? currentPattern.getWindowTime().toMilliseconds() : 0L; + return sinkState; + } - while (currentPattern.getPrevious() != null) { - succeedingPattern = currentPattern; - succeedingState = currentState; - currentPattern = currentPattern.getPrevious(); + private State<T> createMiddleStates(final State<T> sinkState) { - if (!patternNames.add(currentPattern.getName())) { - throw new MalformedPatternException("Duplicate pattern name: " + currentPattern.getName() + ". " + - "Pattern names must be unique."); + State<T> lastSink = sinkState; + while (currentPattern.getPrevious() != null) { + State<T> sourceState; + + checkPatternNameUniqueness(); + + sourceState = new State<>(currentPattern.getName(), State.StateType.Normal); + states.add(sourceState); + usedNames.add(sourceState.getName()); + + if (currentPattern.getQuantifier().isLooping()) { + convertToLooping(lastSink, sourceState); + + if (currentPattern.getQuantifier().isAtLeastOne()) { + sourceState = createFirstMandatoryStateOfLoop( + sourceState, + State.StateType.Normal + ); + states.add(sourceState); + usedNames.add(sourceState.getName()); + } + } else if (currentPattern.getQuantifier() == Quantifier.TIMES) { + sourceState = convertToTimesState(lastSink, sourceState, currentPattern.getTimes()); + } else { + convertToSingletonState( + lastSink, + sourceState); } - Time currentWindowTime = currentPattern.getWindowTime(); + currentPattern = currentPattern.getPrevious(); + lastSink = sourceState; + final Time currentWindowTime = currentPattern.getWindowTime(); if (currentWindowTime != null && currentWindowTime.toMilliseconds() < windowTime) { // the window time is the global minimum of all window times of each state windowTime = currentWindowTime.toMilliseconds(); } + } + + return lastSink; + } - if (states.containsKey(currentPattern.getName())) { - currentState = states.get(currentPattern.getName()); + private void checkPatternNameUniqueness() { + if (usedNames.contains(currentPattern.getName())) { + throw new MalformedPatternException( + "Duplicate pattern name: " + currentPattern.getName() + ". " + + "Pattern names must be unique."); + } + } + + @SuppressWarnings("unchecked") + private State<T> createStartState(State<T> sinkState) { + final State<T> beginningState; + + checkPatternNameUniqueness(); + + if (currentPattern.getQuantifier().isLooping()) { + final State<T> loopingState; + if (currentPattern.getQuantifier().isAtLeastOne()) { + loopingState = new State<>(currentPattern.getName(), State.StateType.Normal); + beginningState = createFirstMandatoryStateOfLoop(loopingState, State.StateType.Start); + states.add(loopingState); } else { - currentState = new State<>(currentPattern.getName(), State.StateType.Normal); - states.put(currentState.getName(), currentState); + loopingState = new State<>(currentPattern.getName(), State.StateType.Start); + beginningState = loopingState; } - - currentState.addStateTransition(new StateTransition<T>( - StateTransitionAction.TAKE, - succeedingState, - (FilterFunction<T>) succeedingPattern.getFilterFunction())); - - if (succeedingPattern instanceof FollowedByPattern) { - // the followed by pattern entails a reflexive ignore transition - currentState.addStateTransition(new StateTransition<T>( - StateTransitionAction.IGNORE, - currentState, - null - )); + convertToLooping(sinkState, loopingState); + } else if (currentPattern.getQuantifier() == Quantifier.TIMES) { + if (currentPattern.getTimes() > 1) { + final State<T> timesState = new State<>(currentPattern.getName(), State.StateType.Normal); + states.add(timesState); + sinkState = convertToTimesState(sinkState, timesState, currentPattern.getTimes() - 1); } + beginningState = new State<>(currentPattern.getName(), State.StateType.Start); + beginningState.addTake(sinkState, (FilterFunction<T>) currentPattern.getFilterFunction()); + } else { + beginningState = new State<>(currentPattern.getName(), State.StateType.Start); + beginningState.addTake(sinkState, (FilterFunction<T>) currentPattern.getFilterFunction()); } - // add the beginning state - final State<T> beginningState; + states.add(beginningState); + usedNames.add(beginningState.getName()); + + return beginningState; + } + + private State<T> convertToTimesState(State<T> sinkState, State<T> sourceState, int times) { + convertToSingletonState(sinkState, sourceState); --- End diff -- Here I have 3 comments: 1) you can create local variables instead of reusing `sourceState` and `sinkState`. 2) you can add a check like `Preconditions.checkArgument(currentPattern.getQuantifier() == Quantifier.TIMES)` 3) currently we cannot have `OPTIONAL` and `TIMES` but the code seems to support that. Am I correct? In this case we could also have in the `Pattern` a method called `atMost(int times)` which will allow the user to specify such a pattern. What do you think?
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