Hi Fritz, this seems to be a bug caused by some leftover (overeager) check. The EvictingWindowOperator in fact has the code to deal with merging windows.
I opened this issue to track the bug: https://issues.apache.org/jira/browse/FLINK-5933. As a workaround, you can use a purging Trigger. You can turn any trigger into a purging trigger using PurgingTrigger.of(<my trigger>). When you do this, the window contents will be cleaned after every window firing. Best, Aljoscha On Mon, 27 Feb 2017 at 19:12 Fritz Budiyanto <fbudi...@icloud.com> wrote: > Hi All, > > How do I evict elements from EventTimeSessionWindow ? > > My use case as follow: I have a long duration session window, and I’d like > to do some processing on every minute and perform regular sink. I use > ContinuousEventTimeTrigger to do the job, as the session could last for > hours (or even days) where large number of new elements kept on coming in. > > I’d like to evict these elements which I already processed from the > previous trigger. Evicting elements is necessary for us to release unused > large number of elements which already processed in the previous trigger, > and also we don’t want to continuously processing these elements over and > over again through out the continuous trigger. I tried to set evictor, but > it is not allowed for MergingWindow type. > > Any thought, comments, or suggestions ? > > Thanks, > > — > Fritz > >