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https://issues.apache.org/jira/browse/FLINK-7169?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16119856#comment-16119856
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ASF GitHub Bot commented on FLINK-7169:
---------------------------------------
Github user dawidwys commented on a diff in the pull request:
https://github.com/apache/flink/pull/4331#discussion_r132169303
--- Diff:
flink-libraries/flink-cep/src/main/java/org/apache/flink/cep/nfa/compiler/NFACompiler.java
---
@@ -150,6 +160,59 @@ long getWindowTime() {
}
/**
+ * Check pattern after match skip strategy.
+ */
+ private void checkPatternSkipStrategy() {
+ AfterMatchSkipStrategy afterMatchSkipStrategy =
currentPattern.getAfterMatchSkipStrategy();
+ if (afterMatchSkipStrategy.getStrategy() ==
AfterMatchSkipStrategy.SkipStrategy.SKIP_TO_FIRST ||
+ afterMatchSkipStrategy.getStrategy() ==
AfterMatchSkipStrategy.SkipStrategy.SKIP_TO_LAST) {
+ Pattern<T, ?> pattern = currentPattern;
+ while
(!pattern.getName().equals(afterMatchSkipStrategy.getPatternName())) {
+ pattern = pattern.getPrevious();
+ }
+ // pattern name match check.
+ if (pattern == null) {
--- End diff --
It is always true. If `pattern.getPrevious` is `null`. The `while` loop
will throw `NullPointerException`.
Missing test for this case.
> 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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