[
https://issues.apache.org/jira/browse/FLINK-7292?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16106007#comment-16106007
]
Yueting Chen commented on FLINK-7292:
-------------------------------------
Hi [~litrain],
Thanks for bringing it up. But I don't think the result should contain an empty
match in your example. In general, {{a?}} means we should try to find a single
match for {{a}} first, if it fails, then an empty result should be generated. I
think for the match pattern {{a?}} and the input events {{b1,a1}} , the result
should be {{\[empty match],a1}}.
IMO, the only meaning that empty result exists is that it indicates how many
match times was processed. Maybe in some use cases it is useful.
> Fix EMPTY MATCH bug in CEP.
> ---------------------------
>
> Key: FLINK-7292
> URL: https://issues.apache.org/jira/browse/FLINK-7292
> Project: Flink
> Issue Type: New Feature
> 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.
--
This message was sent by Atlassian JIRA
(v6.4.14#64029)
