文档中对"Contiguity within looping patterns "的描述是否正确？

Question

作为flink CEP文档中的描述:

1. Strict Contiguity:期望所有匹配的事件严格一个接一个地出现，中间没有任何不匹配的事件。
2. Relaxed Contiguity:忽略在匹配事件之间出现的非匹配事件。
3. Non-Deterministic Relaxed Contiguity:进一步放松连续性，允许额外的匹配忽略一些匹配事件。

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第一个例子很容易理解:

给出模式:"a b"

和输入"a", "c", "b1", "b2"

1. 严格连续输出:{} (no match)
2. 松散邻接输出:{a b1}
3. 非确定性松弛邻接输出:{a b1}, {a b2}

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但是Contiguity within looping patterns的例子真的很难理解:

给定模式:"a b+ c".

和输入:"a", "b1", "d1", "b2", "d2", "b3" "c"

1. 严格连续:{a b3 c}
2. 松弛连续度:{a b1 c}， {a b1 b2 c}， {a b1 b2 b3 c}， {a b2 c}， {a b2 b3 c}， {a b3 c}
3. 非确定性松弛连续:{a b1 c}， {a b1 b2 c}， {a b1 b3 c}， {a b1 b2 b3 c}， {a b2 b2 c}， {a b2 b3 c}， {a b3 c}

the Strict Contiguity output {a b3 c}，但这与Strict Contiguity中的描述相反，因为在a和b3之间有许多non-matching events。

Answer 1

我相信你是对的。在严格的连续性下，它根本不匹配。我写了下面的例子来确保:

public class StreamingJob {
public static void main(String[] args) throws Exception {
StreamExecutionEnvironment env = StreamExecutionEnvironment.getExecutionEnvironment();
DataStream<String> events = env.fromElements("a", "b1", "d1", "b2", "d2", "b3", "c");
AfterMatchSkipStrategy skipStrategy = AfterMatchSkipStrategy.skipPastLastEvent();
Pattern<String, String> pattern =
Pattern.<String>begin("a", skipStrategy)
.where(
new SimpleCondition<String>() {
@Override
public boolean filter(String element) throws Exception {
return element.startsWith("a");
}
})
.next("b+")
.where(
new SimpleCondition<String>() {
@Override
public boolean filter(String element) throws Exception {
return element.startsWith("b");
}
})
.oneOrMore().consecutive()
.next("c")
.where(
new SimpleCondition<String>() {
@Override
public boolean filter(String element) throws Exception {
return element.startsWith("c");
}
});
PatternStream<String> patternStream = CEP.pattern(events, pattern).inProcessingTime();
patternStream.select(new SelectSegment()).addSink(new PrintSinkFunction<>(true));
env.execute();
}
public static class SelectSegment implements PatternSelectFunction<String, String> {
public String select(Map<String, List<String>> pattern) {
return String.join("", pattern.get("a"))
+ String.join("", pattern.get("b+"))
+ String.join("", pattern.get("c"));
}
}
}

我已经创建了FLINK-27456来跟踪这个。