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From Hequn Cheng <chenghe...@gmail.com>
Subject Re: Rich and incrementally aggregating window functions
Date Thu, 09 May 2019 02:07:00 GMT
Hi,

There is a discussion about this before, you can take a look at it[1].
Best, Hequn

[1]
http://apache-flink-user-mailing-list-archive.2336050.n4.nabble.com/Regarding-implementation-of-aggregate-function-using-a-ProcessFunction-td23473.html#a23531

On Thu, May 9, 2019 at 5:14 AM an0 <an00na@gmail.com> wrote:

> I want to use ProcessWindowFunction.Context#globalState in my window
> function. But I don't want to apply ProcessWindowFunction directly to my
> WindowedStream because I don't want to buffer all the elements of each
> window. Currently I'm using WindowedStream#aggregate(AggregateFunction,
> ProcessWindowFunction).
>
> My understanding is that RichFunction.runtimeContext also give access to
> those global states. That thought naturally pointed me to
> RichAggregateFunction, RichReduceFunction and RichFoldFunction. However,
> they all cause runtime error like this:
> "AggregateFunction can not be a RichFunction. Please use
> fold(AggregateFunction, WindowFunction) instead."
>
> So how can I use an incrementally aggregating window function and have
> access to global states at the same time?
>

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