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From Hequn Cheng <chenghe...@gmail.com>
Subject Re: Confused window operation
Date Wed, 14 Nov 2018 06:17:11 GMT
Hi Jeff,

The window is not a global window. It is related to a specified key. You
would have 6 windows after flatMap() and keyBy().
key: hello with 3 windows
key: world with 1 window
key: flink with 1 window
key: hadoop with 1 window

Best, Hequn


On Wed, Nov 14, 2018 at 10:31 AM Jeff Zhang <zjffdu@gmail.com> wrote:

> Hi all,
>
> I am a little confused with the following windows operation. Here's the
> code,
>
> val senv = StreamExecutionEnvironment.getExecutionEnvironment
> senv.setParallelism(1)
> val data = senv.fromElements("hello world", "hello flink", "hello hadoop")
>
> data.flatMap(line => line.split("\\s"))
>   .map(w => (w, 1))
>   .keyBy(0)
>   .countWindow(2, 1)
>   .sum(1)
>   .print("******************")
>
> senv.execute()
>
>
> And this is the output:
>
> ******************> (hello,1)
> ******************> (world,1)
> ******************> (hello,2)
> ******************> (flink,1)
> ******************> (hello,2)
> ******************> (hadoop,1)
>
>
> As my understanding, here we have 3 windows.
>
> window 1
>
> (hello, world)
>
> window 2
>
> (hello, world)
>
> (hello, flink)
>
> window 3
>
> (hello flink)
>
> (hello hadoop)
>
> So for the first window, we have output (hello, 1) (world, 1)
>
> for the second window we should output (hello, 2), (world,1 ), (flink, 1)
>
> for the third window we should have output (hello, 2), (flink, 1), (hadoop, 1)
>
>
> But as you can see, in the above I get different result, do I misunderstand the window
? Could anyone help me to understand that ? Thanks
>
>

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