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From "ASF GitHub Bot (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (FLINK-5968) Document WindowedStream.aggregate()
Date Sun, 22 Oct 2017 15:05:00 GMT

    [ https://issues.apache.org/jira/browse/FLINK-5968?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16214336#comment-16214336

ASF GitHub Bot commented on FLINK-5968:

Github user bowenli86 commented on a diff in the pull request:

    --- Diff: docs/dev/stream/operators/windows.md ---
    @@ -427,6 +427,93 @@ input
     The above example sums up the second fields of the tuples for all elements in a window.
    +### AggregateFunction
    +An `AggregateFunction` is a generalized version of a `ReduceFunction` that has three
types: an
    +input type (`IN`), accumulator type (`ACC`), and an output type (`OUT`). The input type
is the type
    +of elements in the input stream and the `AggregateFunction` has a method for adding one
    +element to an accumulator. The interface also has methods for creating an initial accumulator,
    +for merging two accumulators into one accumulator and for extracting an output (of type
`OUT`) from
    +an accumulator. We will see how this works in the example below.
    +Same as with `ReduceFunction`, Flink will incrementally aggregate input elements of a
window as they
    +A `AggregateFunction` can be defined and used like this:
    --- End diff --

> Document WindowedStream.aggregate()
> -----------------------------------
>                 Key: FLINK-5968
>                 URL: https://issues.apache.org/jira/browse/FLINK-5968
>             Project: Flink
>          Issue Type: Sub-task
>          Components: DataStream API, Documentation
>            Reporter: Aljoscha Krettek
>            Assignee: Aljoscha Krettek
>            Priority: Blocker
>             Fix For: 1.4.0

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