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https://issues.apache.org/jira/browse/FLINK-6420?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Flink Jira Bot updated FLINK-6420:
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Labels: stale-minor (was: )
> Cleaner CEP API to specify conditions between events
> ----------------------------------------------------
>
> Key: FLINK-6420
> URL: https://issues.apache.org/jira/browse/FLINK-6420
> Project: Flink
> Issue Type: Improvement
> Components: Library / CEP
> Affects Versions: 1.3.0
> Reporter: Elias Levy
> Priority: Minor
> Labels: stale-minor
>
> Flink 1.3 will introduce so-called iterative conditions, which allow the
> predicate to look up events already matched by conditions in the pattern.
> This permits specifying conditions between matched events, similar to a
> conditional join between tables in SQL. Alas, the API could be simplified to
> specify such conditions more declaratively.
> At the moment you have to do something like
> {code}
> Pattern.
> .begin[Foo]("first")
> .where( first => first.baz == 1 )
> .followedBy("next")
> .where({ (next, ctx) =>
> val first = ctx.getEventsForPattern("first").next
> first.bar == next.bar && next => next.boo = "x"
> })
> {code}
> which is not very clean. It would friendlier if you could do something like:
> {code}
> Pattern.
> .begin[Foo]("first")
> .where( first => first.baz == 1 )
> .followedBy("next")
> .relatedTo("first", { (first, next) => first.bar == next.bar })
> .where( next => next.boo = "x" )
> {code}
> Something along these lines would work well when the condition being tested
> against matches a single event (single quantifier).
> If the condition being tested can accept multiple events (e.g. times
> quantifier) two other methods could be used {{relatedToAny}} and
> {{relatedToAll}}, each of which takes a predicate function. In both cases
> each previously accepted element of the requested condition is evaluated
> against the predicate. In the former case if any evaluation returns true the
> condition is satisfied. In the later case all evaluations must return true
> for the condition to be satisfied.
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