[
https://issues.apache.org/jira/browse/FLINK-7147?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16116461#comment-16116461
]
ASF GitHub Bot commented on FLINK-7147:
---------------------------------------
Github user dawidwys commented on the issue:
https://github.com/apache/flink/pull/4296
There is also one more problem. When we have optional after `greedy` it
does not work well. E.g. have a look at this test case:
@Test
public void testGreedyZeroOrMoreBeforeOptional2() {
List<StreamRecord<Event>> inputEvents = new ArrayList<>();
Event c = new Event(40, "c", 1.0);
Event a1 = new Event(41, "a", 2.0);
Event a2 = new Event(42, "a", 2.0);
Event d = new Event(43, "d", 3.0);
Event a3 = new Event(42, "a", 2.0);
Event e = new Event(44, "e", 3.0);
inputEvents.add(new StreamRecord<>(c, 1));
inputEvents.add(new StreamRecord<>(a1, 2));
inputEvents.add(new StreamRecord<>(a2, 3));
inputEvents.add(new StreamRecord<>(d, 4));
inputEvents.add(new StreamRecord<>(a3, 5));
inputEvents.add(new StreamRecord<>(e, 6));
// c a* d e
Pattern<Event, ?> pattern =
Pattern.<Event>begin("start").where(new SimpleCondition<Event>() {
private static final long serialVersionUID =
5726188262756267490L;
@Override
public boolean filter(Event value) throws Exception {
return value.getName().equals("c");
}
}).followedBy("middle1").where(new SimpleCondition<Event>() {
private static final long serialVersionUID =
5726188262756267490L;
@Override
public boolean filter(Event value) throws Exception {
return value.getName().equals("a");
}
}).oneOrMore().optional().greedy().followedBy("middle2").where(new
SimpleCondition<Event>() {
private static final long serialVersionUID =
5726188262756267490L;
@Override
public boolean filter(Event value) throws Exception {
return value.getName().equals("d");
}
}).optional().followedBy("end").where(new
SimpleCondition<Event>() {
private static final long serialVersionUID =
5726188262756267490L;
@Override
public boolean filter(Event value) throws Exception {
return value.getName().equals("e");
}
});
NFA<Event> nfa = NFACompiler.compile(pattern,
Event.createTypeSerializer(), false);
final List<List<Event>> resultingPatterns =
feedNFA(inputEvents, nfa);
compareMaps(resultingPatterns, Lists.<List<Event>>newArrayList(
Lists.newArrayList(c, a1, a2, a3, e),
Lists.newArrayList(c, a1, a2, d, e)
));
}
Right know it also returns `c a1 a2 e`, which I think is not correct. I
don't think there is an easy way to fix it right now. I would suggest
restricting on the Pattern level that greedy must not be followed by an
`Optional` patten. I would like to hear opinions on that, @kl0u.
> Support greedy quantifier in CEP
> --------------------------------
>
> Key: FLINK-7147
> URL: https://issues.apache.org/jira/browse/FLINK-7147
> Project: Flink
> Issue Type: Sub-task
> Components: CEP, Table API & SQL
> Reporter: Dian Fu
> Assignee: Dian Fu
>
> Greedy quantifier will try to match the token as many times as possible. For
> example, for pattern {{a b* c}} (skip till next is used) and inputs {{a b1 b2
> c}}, if the quantifier for {{b}} is greedy, it will only output {{a b1 b2 c}}.
--
This message was sent by Atlassian JIRA
(v6.4.14#64029)
