[jira] [Commented] (FLINK-7292) Fix EMPTY MATCH bug in CEP.

["Dawid Wysakowicz (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/FLINK-7292?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16104917#comment-16104917 ] 

Dawid Wysakowicz commented on FLINK-7292:
-----------------------------------------

I would not say it is a bug. It is a architectural choice not to return empty results. I personally don't see any value in such results.

> Fix EMPTY MATCH bug in CEP.
> ---------------------------
>
>                 Key: FLINK-7292
>                 URL: https://issues.apache.org/jira/browse/FLINK-7292
>             Project: Flink
>          Issue Type: Bug
>          Components: CEP
>            Reporter: zhangxiaoyu
>
> Currently, with the pattern {quote}a? {quote}and the event{quote} a1{quote}, the result pattern is only {quote} {a1}{quote}, without the empty match.
> We wish the empty matched is also returned. And I am working on this issue now.
> My method is  checking if there exists empty match only when the the first event comes(at the StartState) ——try to traverse the PROCEED edges with the trueFunction condition from the StartState, see if it can arrive FinalState, if so, add an empty list to the result.



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