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https://issues.apache.org/jira/browse/FLINK-8914?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16394222#comment-16394222
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David Anderson commented on FLINK-8914:
---------------------------------------

This bug was also reported on Stackoverflow: 
https://stackoverflow.com/questions/48028061/flink-cep-greedy-matching

> CEP's greedy() modifier doesn't work
> ------------------------------------
>
>                 Key: FLINK-8914
>                 URL: https://issues.apache.org/jira/browse/FLINK-8914
>             Project: Flink
>          Issue Type: Bug
>          Components: CEP
>    Affects Versions: 1.4.0, 1.4.1
>            Reporter: David Anderson
>            Priority: Major
>
> When applied to the first or last component of a CEP Pattern, greedy() 
> doesn't work correctly. Here's an example:
> {code:java}
> package com.dataartisans.flinktraining.exercises.datastream_java.cep;
> import org.apache.flink.cep.CEP;
> import org.apache.flink.cep.PatternSelectFunction;
> import org.apache.flink.cep.PatternStream;
> import org.apache.flink.cep.pattern.Pattern;
> import org.apache.flink.cep.pattern.conditions.SimpleCondition;
> import org.apache.flink.streaming.api.datastream.DataStream;
> import org.apache.flink.streaming.api.environment.StreamExecutionEnvironment;
> import java.util.List;
> import java.util.Map;
> public class RunLength {
>   public static void main(String[] args) throws Exception {
>     StreamExecutionEnvironment env = 
> StreamExecutionEnvironment.getExecutionEnvironment();
>     env.setParallelism(1);
>     DataStream<Integer> input = env.fromElements(1, 1, 1, 1, 1, 0, 1, 1, 1, 
> 0);
>     Pattern<Integer, ?> onesThenZero = Pattern.<Integer>begin("ones")
>       .where(new SimpleCondition<Integer>() {
>         @Override
>         public boolean filter(Integer value) throws Exception {
>           return value == 1;
>         }
>       })
>       .oneOrMore()
>       .greedy()
>       .consecutive()
>       .next("zero")
>       .where(new SimpleCondition<Integer>() {
>         @Override
>         public boolean filter(Integer value) throws Exception {
>           return value == 0;
>         }
>       });
>       PatternStream<Integer> patternStream = CEP.pattern(input, onesThenZero);
>       // Expected: 5 3
>       // Actual: 5 4 3 2 1 3 2 1
>       patternStream.select(new LengthOfRun()).print();
>       env.execute();
>     }
>     public static class LengthOfRun implements PatternSelectFunction<Integer, 
> Integer> {
>       public Integer select(Map<String, List<Integer>> pattern) {
>       return pattern.get("ones").size();
>     }
>   }
> }
> {code}
> The only workaround for now seems to be to rewrite the pattern so that 
> greedy() isn't needed – i.e. by bracketing the greedy section with a prefix 
> and suffix that both have to be matched.



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