Hi Puneet,
Sorry I'm not be an expert for CEP, but the underlying implementation of the
CEP should
be based on the NFA, and from the API documentation, `followedBy` does not
require the
two patterns are adjacent (namely the give pattern also accepts ['a', 'c',
'b']. Thus when
recieved 'a', I think the NFA might have two possible transitions, one is to
accept 'b'
and get a match, another one is to ignore 'b' and waiting for the following
events, thus
the condition might be eval for two times.
Best,
Yun
------------------Original Mail ------------------
Sender:Schwalbe Matthias <matthias.schwa...@viseca.ch>
Send Date:Wed Oct 27 17:55:18 2021
Recipients:Puneet Duggal <puneetduggal1...@gmail.com>, user
<user@flink.apache.org>
Subject:RE: Duplicate Calls to Cep Filter
Hi Puneet,
… not able to answer your question, but I would be curious to also print out
the value with your diagnostic message.
… assuming we’ll see an ‘a’ and a ‘b’ for both filters resp.
… simple explanation would be that the filters are applied to all input,
regardless of the pattern matching that follow the input filtering (just
guessing)
Thias
From: Puneet Duggal <puneetduggal1...@gmail.com>
Sent: Mittwoch, 27. Oktober 2021 11:12
To: user <user@flink.apache.org>
Subject: Duplicate Calls to Cep Filter
Hi,
I am facing an issue where a single event is causing execution of a cep filter
multiple times. I went through this video explaining automata formation from
pattern sequence but it still does not explain the behaviour that I am facing.
Following is the sample pattern for whichI am testing this behaviour.
Pattern<String, ?> innerPattern =
Pattern
.<String>begin("start")
.where(new SimpleCondition<String>() {
@Override
public boolean filter(String value) throws
Exception {
System.out.println("In the beginning");
return value.equals("a");
}
})
.followedBy("middle")
.where(new SimpleCondition<String>() {
@Override
public boolean filter(String value) throws
Exception {
System.out.println("In the middle");
return value.equals("b");
}
});
On passing events a and b to this pattern.. result is
1> a
In the beginning
1> b
In the middle
In the middle
In the beginning
Matched
3> {start=[a], middle=[b]}
As you can see ... on ingestion of b middle pattern is getting called twice.
Any ideas of this behaviour.
Thanks and regards,
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