[jira] [Commented] (FLINK-7147) Support greedy quantifier in CEP

["ASF GitHub Bot (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/FLINK-7147?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16108520#comment-16108520 ] 

ASF GitHub Bot commented on FLINK-7147:
---------------------------------------

Github user dawidwys commented on a diff in the pull request:

    https://github.com/apache/flink/pull/4296#discussion_r130537682
  
    --- Diff: flink-libraries/flink-cep/src/main/java/org/apache/flink/cep/nfa/compiler/NFACompiler.java ---
    @@ -657,25 +663,34 @@ private boolean isPatternOptional(Pattern<T, ?> pattern) {
     				true);
     
     			IterativeCondition<T> proceedCondition = getTrueFunction();
    -			if (currentPattern.getQuantifier().isGreedy()) {
    -				proceedCondition = getGreedyCondition(proceedCondition, Lists.newArrayList(takeCondition));
    +			if (currentPattern.getQuantifier().hasProperty(Quantifier.QuantifierProperty.GREEDY)) {
    +				proceedCondition = getGreedyCondition(
    +					proceedCondition,
    +					takeCondition,
    +					ignoreCondition,
    +					followingTakeCondition);;
     			}
     			final State<T> loopingState = createState(currentPattern.getName(), State.StateType.Normal,
    -				currentPattern.getQuantifier().isGreedy());
    +				currentPattern.getQuantifier().hasProperty(Quantifier.QuantifierProperty.GREEDY));
     			loopingState.addProceed(sinkState, proceedCondition);
     			loopingState.addTake(takeCondition);
     
     			addStopStateToLooping(loopingState);
     
     			if (ignoreCondition != null) {
     				final State<T> ignoreState = createState(currentPattern.getName(), State.StateType.Normal,
    -					currentPattern.getQuantifier().isGreedy());
    +					currentPattern.getQuantifier().hasProperty(Quantifier.QuantifierProperty.GREEDY));
     				ignoreState.addTake(loopingState, takeCondition);
     				ignoreState.addIgnore(ignoreCondition);
     				loopingState.addIgnore(ignoreState, ignoreCondition);
    +				if (currentPattern.getQuantifier().hasProperty(Quantifier.QuantifierProperty.GREEDY)) {
    --- End diff --
    
    I think the problem you mentioned with `GreedyITCase.testGreedyZeroOrMoreBeforeOptional2` is due to that proceed. The whole reason behind the additional ignoreState was for it not to have the `PROCEED` transition as it creates additional computationStates with the `sinkState`. I think for the greedy to work we need to put customized ignoreCondition into the `sinkState` of a greedy Pattern. What do you think?


> Support greedy quantifier in CEP
> --------------------------------
>
>                 Key: FLINK-7147
>                 URL: https://issues.apache.org/jira/browse/FLINK-7147
>             Project: Flink
>          Issue Type: Sub-task
>          Components: CEP, Table API & SQL
>            Reporter: Dian Fu
>            Assignee: Dian Fu
>
> Greedy quantifier will try to match the token as many times as possible. For example, for pattern {{a b* c}} (skip till next is used) and inputs {{a b1 b2 c}}, if the quantifier for {{b}} is greedy, it will only output {{a b1 b2 c}}.



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