Elias Levy created FLINK-6418:
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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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