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From "Elias Levy (JIRA)" <j...@apache.org>
Subject [jira] [Created] (FLINK-6418) Support for dynamic state changes in CEP patterns
Date Fri, 28 Apr 2017 23:26:04 GMT
Elias Levy created FLINK-6418:
---------------------------------

             Summary: Support for dynamic state changes in CEP patterns
                 Key: FLINK-6418
                 URL: https://issues.apache.org/jira/browse/FLINK-6418
             Project: Flink
          Issue Type: Improvement
          Components: CEP
    Affects Versions: 1.3.0
            Reporter: Elias Levy


Flink CEP library allows one to define event pattern to match where the match condition can
be determined programmatically via the {{where}} method.  Flink 1.3 will introduce so-called
iterative conditions, which allow the predicate to look up events already matched by the pattern
and thus be conditional on them.

1.3 also introduces to the API quantifer methods which allow one to declaratively specific
how many times a condition must be matched before there is a state change.

Alas, there are use cases where the quantifier must be determined dynamically based on the
events matched by the pattern so far.  Therefore, I propose the adding of a new {{Pattern}}:
{{until}}.

Like the new iterative variant of {{where}}, {{until}} would take a predicate function and
a context that provides access to events already matched.  But whereas {{where}} determines
if an event is accepted by the pattern, {{until}} determines whether is pattern should move
on to the next state.

In our particular use case, we have a pattern where an event is matched a number of times,
but depending on the event type, the number (threshold) for the pattern to match is different.
 We could decompose the pattern into multiple similar patterns, but that could be inefficient
if we have many such patterns.  If the functionality of {{until}} were available, we could
make do with a single pattern.





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