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https://issues.apache.org/jira/browse/FLINK-3703?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15428300#comment-15428300
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ASF GitHub Bot commented on FLINK-3703:
---------------------------------------
Github user tillrohrmann commented on a diff in the pull request:
https://github.com/apache/flink/pull/2367#discussion_r75496232
--- Diff:
flink-libraries/flink-cep/src/main/java/org/apache/flink/cep/pattern/Pattern.java
---
@@ -129,6 +141,23 @@ public Time getWindowTime() {
}
/**
+ * Set a matching behaviour that defines if the same event can be used
in multiple matching sequences.
+ *
+ * @param matchingBehaviour New matching behaviour
+ * @return The same pattern operator with the specified matching
behaviour
+ */
+ public Pattern<T, F> matchingBehaviour(MatchingBehaviour
matchingBehaviour) {
+
+ Pattern<T, F> pattern = this;
+ while (pattern != null) {
+ pattern.matchingBehaviour = matchingBehaviour;
+ pattern = (Pattern<T, F>) pattern.getPrevious();
+ }
+
+ return this;
--- End diff --
Looking at the necessary implementation to wire the matching behaviour
through all `Pattern` instances, I wonder whether the `MatchingBehaviour`
should rather be given to the `CEP.pattern` call. There it could be given to
the generated `NFA` which is responsible for making sure that the behaviour is
respected. The API would then look like:
`CEP.pattern(input, pattern, matchingBehaviour)`
What do you think?
> Add sequence matching semantics to discard matched events
> ---------------------------------------------------------
>
> Key: FLINK-3703
> URL: https://issues.apache.org/jira/browse/FLINK-3703
> Project: Flink
> Issue Type: Improvement
> Components: CEP
> Affects Versions: 1.0.0, 1.1.0
> Reporter: Till Rohrmann
> Assignee: Ivan Mushketyk
> Priority: Minor
>
> There is no easy way to decide whether events can be part of multiple
> matching sequences or not. Currently, the default is that an event can
> participate in multiple matching sequences. E.g. if you have the pattern
> {{Pattern.<Event>begin("a").followedBy("b")}} and the input event stream
> {{Event("A"), Event("B"), Event("C")}}, then you will generate the following
> matching sequences: {{Event("A"), Event("B")}}, {{Event("A"), Event("C")}}
> and {{Event("B"), Event("C")}}.
> It would be useful to allow the user to define where the matching algorithm
> should continue after a matching sequence has been found. Possible option
> values could be
> * {{from first}} - continue keeping all events for future matches (that is
> the current behaviour)
> * {{after first}} - continue after the first element (remove first matching
> event and continue with the second event)
> * {{after last}} - continue after the last element (effectively discarding
> all elements of the matching sequence)
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