[jira] [Commented] (FLINK-7293) Support custom order by in PatternStream

["ASF GitHub Bot (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/FLINK-7293?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16110557#comment-16110557 ] 

ASF GitHub Bot commented on FLINK-7293:
---------------------------------------

Github user dawidwys commented on a diff in the pull request:

    https://github.com/apache/flink/pull/4418#discussion_r130816980
  
    --- Diff: flink-libraries/flink-cep/src/main/java/org/apache/flink/cep/operator/AbstractKeyedCEPPatternOperator.java ---
    @@ -257,7 +289,32 @@ public void onEventTime(InternalTimer<KEY, VoidNamespace> timer) throws Exceptio
     
     	@Override
     	public void onProcessingTime(InternalTimer<KEY, VoidNamespace> timer) throws Exception {
    -		// not used
    +		NFA<IN> nfa = getNFA();
    +
    +		// emit the events in order
    +		for (IN event : sort(bufferedEvents.get())) {
    +			processEvent(nfa, event, getProcessingTimeService().getCurrentProcessingTime());
    +		}
    +
    +		// remove all buffered rows
    +		bufferedEvents.clear();
    +
    +		updateNFA(nfa);
    +	}
    +
    +	private Iterable<IN> sort(Iterable<IN> iter) {
    +		if (comparator == null) {
    +			return iter;
    +		} else {
    +			// insert all events into the sort buffer
    +			List<IN> sortBuffer = new ArrayList<>();
    --- End diff --
    
    As we dropped support of Java 7, we could use `Stream` here. That way we won't need to create the temporary buffer.
    
    Sth like:
    
    	private Stream<IN> sort(Iterable<IN> iter) {
    		Stream<IN> stream = StreamSupport.stream(iter.spliterator(), false);
    		if (comparator == null) {
    			return stream;
    		} else {
    			return stream.sorted(comparator);
        }
    
    And use it like this:
    
    	sort(bufferedEvents.get()).forEachOrdered(
    		event -> processEvent(nfa, event, getProcessingTimeService().getCurrentProcessingTime())
    	);
    
    What do you think?


> Support custom order by in PatternStream
> ----------------------------------------
>
>                 Key: FLINK-7293
>                 URL: https://issues.apache.org/jira/browse/FLINK-7293
>             Project: Flink
>          Issue Type: Sub-task
>          Components: CEP
>            Reporter: Dian Fu
>            Assignee: Dian Fu
>
> Currently, when {{ProcessingTime}} is configured, the events are fed to NFA in the order of the arriving time and when {{EventTime}} is configured, the events are fed to NFA in the order of the event time. It should also allow custom {{order by}} to allow users to define the order of the events besides the above factors.



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