0

我正在和 Flink CEP 贪婪的算子打架。

鉴于以下java代码：

    final StreamExecutionEnvironment env = StreamExecutionEnvironment.getExecutionEnvironment();

    List<String> strings = Arrays.asList("1,3,5,5,5,5,6,".split(","));

    DataStream<String> input = env.fromCollection(strings);

    Pattern<String, ?> pattern = Pattern.<String>
    begin("start").where(new SimpleCondition<String>() {
        @Override
        public boolean filter(String value) throws Exception {
            return value.equals("5");
        }
    }).oneOrMore().greedy()
    .followedBy("end").where(new SimpleCondition<String>() {

        @Override
        public boolean filter(String value) throws Exception {
            return value.equals("6");
        }
    });

    PatternStream<String> patternStream = CEP.pattern(input, pattern);

    DataStream<String> result = patternStream.select(new PatternSelectFunction<String, String>() {
        @Override
        public String select(Map<String, List<String>> pattern) throws Exception {
            System.err.println("=======");
            pattern.values().forEach(match -> match.forEach(event -> System.err.println(event)));
            System.err.println("=======");
            return "-";
        }
    });

    result.print();
    env.execute("Flink Streaming Java API Skeleton");

我想看看：只发出“5 5 5 5 6”

但是，它匹配“5 5 5 5 6”、“5 5 5 6”、“5 5 6”、“5 6”

如果我做：

    begin("start").where(new SimpleCondition<String>() {
        @Override
        public boolean filter(String value) throws Exception {
            return value.equals("3");
        }
    }).followedBy("middle").where(new SimpleCondition<String>() {
        @Override
        public boolean filter(String value) throws Exception {
            return value.equals("5");
        }
    }).oneOrMore().greedy()
    .followedBy("end").where(new SimpleCondition<String>() {

        @Override
        public boolean filter(String value) throws Exception {
            return value.equals("6");
        }
    });

但是，（因此提供不同的起始匹配）Greedy 运算符通过发出“3 5 5 5 5 6”按预期工作。

是否有可能让一个贪婪的匹配器在没有不同起始模式的情况下抓取所有匹配项？

还是我错过了什么？

斯蒂芬

4

2 回答 2

1

感谢 Chesnay Schepler 的上述评论：

有一个关于贪婪匹配的已知错误可以解释该行为：issues.apache.org/jira/browse/FLINK-8914

我会暂时将此作为答案。

于 2018-05-03T18:03:45.323 回答
0

要控制将分配给事件的匹配数，您需要指定称为 AfterMatchSkipStrategy 的跳过策略。

使用 Pattern.begin("start", AfterMatchSkipStrategy.skipPastLastEvent())

final StreamExecutionEnvironment env = StreamExecutionEnvironment.getExecutionEnvironment();

List<String> strings = Arrays.asList("1,3,5,5,5,5,6,".split(","));

DataStream<String> input = env.fromCollection(strings);

Pattern<String, ?> pattern = Pattern.<String>
        begin("start", AfterMatchSkipStrategy.skipPastLastEvent()).where(new SimpleCondition<String>() {
  @Override
  public boolean filter(String value) throws Exception {
    return value.equals("5");
  }
}).oneOrMore().greedy()
        .followedBy("end").where(new SimpleCondition<String>() {
          @Override
          public boolean filter(String value) throws Exception {
            return value.equals("6");
          }
        });

PatternStream<String> patternStream = CEP.pattern(input, pattern);

DataStream<String> result = patternStream.select(new PatternSelectFunction<String, String>() {
  @Override
  public String select(Map<String, List<String>> pattern) throws Exception {
    System.err.println("=======");
    pattern.values().forEach(match -> match.forEach(event -> System.err.println(event)));
    System.err.println("=======");
    return "-";
  }
});

result.print();
env.execute("Flink Streaming Java API Skeleton");
于 2019-04-02T03:47:57.710 回答