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https://issues.apache.org/jira/browse/FLINK-7169?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16125383#comment-16125383
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ASF GitHub Bot commented on FLINK-7169:
---------------------------------------
Github user kl0u commented on a diff in the pull request:
https://github.com/apache/flink/pull/4331#discussion_r132898814
--- Diff:
flink-libraries/flink-cep/src/main/java/org/apache/flink/cep/nfa/NFA.java ---
@@ -340,6 +362,65 @@ public void resetNFAChanged() {
return Tuple2.of(result, timeoutResult);
}
+ private void
discardComputationStatesAccordingToStrategy(Queue<ComputationState<T>>
computationStates,
--- End diff --
This method is very fragile as it makes the assumption that the different
patterns appear in the match in the order that they were declared in the
pattern declaration, e.g. for a pattern `A -> B -> C` it assumes that the
partial matches will appear in the order [`matches for A`, `matches for B`,
`matches for C`]. This is *NOT* correct as we use a `HashMap` which does not
provide any ordering guarantees.
A quick fix would be to use a `LinkedHashMap` as the return type for the
`extractCurrentMatches` and put the results there in the correct order.
> Support AFTER MATCH SKIP function in CEP library API
> ----------------------------------------------------
>
> Key: FLINK-7169
> URL: https://issues.apache.org/jira/browse/FLINK-7169
> Project: Flink
> Issue Type: Sub-task
> Components: CEP
> Reporter: Yueting Chen
> Assignee: Yueting Chen
> Fix For: 1.4.0
>
>
> In order to support Oracle's MATCH_RECOGNIZE on top of the CEP library, we
> need to support AFTER MATCH SKIP function in CEP API.
> There're four options in AFTER MATCH SKIP, listed as follows:
> 1. AFTER MATCH SKIP TO NEXT ROW: resume pattern matching at the row after the
> first row of the current match.
> 2. AFTER MATCH SKIP PAST LAST ROW: resume pattern matching at the next row
> after the last row of the current match.
> 3. AFTER MATCH SKIP TO FIST *RPV*: resume pattern matching at the first row
> that is mapped to the row pattern variable RPV.
> 4. AFTER MATCH SKIP TO LAST *RPV*: resume pattern matching at the last row
> that is mapped to the row pattern variable RPV.
> I think we can introduce a new function to `CEP` class, which takes a new
> parameter as AfterMatchSKipStrategy.
> The new API may looks like this
> {code}
> public static <T> PatternStream<T> pattern(DataStream<T> input, Pattern<T, ?>
> pattern, AfterMatchSkipStrategy afterMatchSkipStrategy)
> {code}
> We can also make `SKIP TO NEXT ROW` as the default option, because that's
> what CEP library behaves currently.
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