johnyangk commented on a change in pull request #151: [NEMO-267] Consider
watermark holds in GroupByKeyAndWindowDoFnTransform
URL: https://github.com/apache/incubator-nemo/pull/151#discussion_r231353759
##########
File path:
compiler/frontend/beam/src/main/java/org/apache/nemo/compiler/frontend/beam/transform/GroupByKeyAndWindowDoFnTransform.java
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@@ -314,4 +345,31 @@ public TimerInternals timerInternalsForKey(final K key) {
return stateAndTimerForKey.timerInternals;
}
}
+
+ /**
+ * This class wraps the output collector to track the watermark hold of each
key.
+ */
+ final class GBKWOutputCollector implements
OutputCollector<WindowedValue<KV<K, Iterable<InputT>>>> {
+ private final OutputCollector<WindowedValue<KV<K, Iterable<InputT>>>>
outputCollector;
+ GBKWOutputCollector(final OutputCollector<WindowedValue<KV<K,
Iterable<InputT>>>> outputCollector) {
+ this.outputCollector = outputCollector;
+ }
+
+ @Override
+ public void emit(final WindowedValue<KV<K, Iterable<InputT>>> output) {
+ // adds the output timestamp to the watermark hold of each key
+ // +1 to the output timestamp because if the window is [0-5000), the
timestamp is 4999
Review comment:
For an element to belong to a window [0~5000) then its timestamp must be one
of 0, 1, ... , 4999.
If you do +1 to an element with timestamp 4999, would that make the element
belong to a different window [5000, 10000)?
Please let me know if I'm missing something here.
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