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From lofifnc <alexander.k...@mni.thm.de>
Subject Re: Trying to comprehend rolling windows + event time
Date Sat, 20 Feb 2016 16:06:39 GMT
Hi,

You're right, expect that ("grace", "arctic", 25) is emitted with timestamp
90 seconds along with a for watermark 90 seconds.

I followed your advice and implemented a simple window function printing the
start + end of a window along with it's content. You can see that a window
from minute 1 till 6 is emitted containing the ("grace", "arctic", 25)
triple.

window: -4 -> 1 key: (arctic)
(susi,arctic,20)
===================
window: -4 -> 1 key: (elephant)
(hans,elephant,15)
(pete,elephant,40)
===================
window: 1 -> 6 key: (arctic)
(grace,arctic,25)
===================
window: 0 -> 5 key: (elephant)
(hans,elephant,15)
(pete,elephant,40)
===================
window: 0 -> 5 key: (arctic)
(susi,arctic,20)
(grace,arctic,25)
===================
window: -1 -> 4 key: (arctic)
(susi,arctic,20)
(grace,arctic,25)
===================
window: -1 -> 4 key: (elephant)
(hans,elephant,15)
(pete,elephant,40)
===================
window: -2 -> 3 key: (arctic)
(susi,arctic,20)
(grace,arctic,25)
===================
window: -2 -> 3 key: (elephant)
(hans,elephant,15)
(pete,elephant,40)
===================
window: -3 -> 2 key: (arctic)
(susi,arctic,20)
(grace,arctic,25)
===================
window: -3 -> 2 key: (elephant)
(hans,elephant,15)
(pete,elephant,40)
===================

So what basically happens is that the windowing mechanism emits all
unfinished windows when it's closed?
Because based on the watermarks Flink can not decide that, the window 1 -> 6
is finished. 

Best Alex.



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