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Sihua Zhou commented on FLINK-9736: ----------------------------------- Hi [~yuzhih...@gmail.com] AFAIK, {{heapOfKeyGroupHeaps}} will never be empty, as I mentioned above, it created in the constructor of {{KeyGroupPartitionedPriorityQueue}} to maintain the timer structure base on the heap of each key group. The number of elements in heapOfKeyGroupHeaps should be equal to the number of key groups in each Task, but as a double check I think maybe [~stefanrichte...@gmail.com] could help to confirm this. > Potential null reference in KeyGroupPartitionedPriorityQueue#poll() > ------------------------------------------------------------------- > > Key: FLINK-9736 > URL: https://issues.apache.org/jira/browse/FLINK-9736 > Project: Flink > Issue Type: Bug > Reporter: Ted Yu > Assignee: vinoyang > Priority: Minor > > {code} > final PQ headList = heapOfkeyGroupedHeaps.peek(); > final T head = headList.poll(); > {code} > {{peek}} call may return null. > The return value should be checked before de-referencing. -- This message was sent by Atlassian JIRA (v7.6.3#76005)