Github user aljoscha commented on a diff in the pull request:
https://github.com/apache/flink/pull/4665#discussion_r139702816
--- Diff:
flink-streaming-java/src/main/java/org/apache/flink/streaming/runtime/operators/windowing/WindowOperator.java
---
@@ -405,6 +411,8 @@ public void merge(W mergeResult,
// windowAssigner is event time and current timestamp + allowed
lateness no less than element timestamp
if (isSkippedElement && lateDataOutputTag != null &&
isElementLate(element)) {
sideOutput(element);
+ } else if (isSkippedElement) {
--- End diff --
I think we also need to check whether it's late. An element could also be
skipped because no windows were assigned to it.
---
