[jira] [Commented] (FLINK-2144) Implement count, average, and variance for windows

["Gabor Gevay (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/FLINK-2144?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15284473#comment-15284473 ] 

Gabor Gevay commented on FLINK-2144:
------------------------------------

Originally, I wanted to make this calculation incremental both on new elements and on evictions. With the new windowing API, the eviction part lost its importance. However, making it incremental for new elements is still valid, as this would allow making these calculations without buffering up the window. I think this essentially means that these should be implemented in FoldFunctions, which should be automatically pre-aggregated by Flink.

> Implement count, average, and variance for windows
> --------------------------------------------------
>
>                 Key: FLINK-2144
>                 URL: https://issues.apache.org/jira/browse/FLINK-2144
>             Project: Flink
>          Issue Type: Sub-task
>          Components: Streaming
>            Reporter: Gabor Gevay
>            Assignee: Gabor Gevay
>            Priority: Minor
>              Labels: statistics
>
> By count I mean the number of elements in the window.
> These can be implemented very efficiently building on FLINK-2143:
> Store: O(1)
> Evict: O(1)
> emitWindow: O(1)



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