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From Fabian Hueske <fhue...@gmail.com>
Subject Re: Window metadata removal
Date Thu, 05 Sep 2019 10:04:11 GMT
Hi,

A window needs to keep the data as long as it expects new data.
This is clearly the case before the end time of the window was reached. If
my window ends at 12:30, I want to wait (at least) until 12:30 before I
remove any data, right?

In case you expect some data to be late, you can configure allowedLateness.
Let's say, we configure allowedLateness of 10 minutes. In that case, Flink
would keep the metadata of the window that closes at 12:30 until 12:40.
The data is kept to be able to update the result of the window until
allowedLateness has passed.
If we for example receive a late record at 12:38, we can still update the
result of the window because we kept all required data.

If you don't need allowedLateness, don't configure it (the default is 0).

Best, Fabian

Am Mo., 2. Sept. 2019 um 16:46 Uhr schrieb gil bl <gil.bl@yandex.com>:

> Hi,
>
> I'm interested in why metadata like WindowOperator and InternalTimer are
> being kept for windowSize + allowedLateness period per each pane.
>
>    - What is the purpose of keeping this data if no new events are
>    expected to enter the pane?
>    - Is there any way this metadata can be released earlier?
>
>

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