[jira] [Commented] (BEAM-145) OutputTimeFn#assignOutputTime overrides WindowFn#getOutputTime in unfortunate ways

["ASF GitHub Bot (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/BEAM-145?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15359267#comment-15359267 ] 

ASF GitHub Bot commented on BEAM-145:
-------------------------------------

GitHub user kennknowles opened a pull request:

    https://github.com/apache/incubator-beam/pull/573

    [BEAM-145] Fix timestamps in GroupAlsoByWindowsProperties

    Be sure to do all of the following to help us incorporate your contribution
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     - [x] Make sure the PR title is formatted like:
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    ---
    
    Some of the timestamps were not adjusted when [BEAM-145](https://issues.apache.org/jira/browse/BEAM-145) was fixed to respect the `WindowFn`'s timestamps.

You can merge this pull request into a Git repository by running:

    $ git pull https://github.com/kennknowles/incubator-beam GABWProperties

Alternatively you can review and apply these changes as the patch at:

    https://github.com/apache/incubator-beam/pull/573.patch

To close this pull request, make a commit to your master/trunk branch
with (at least) the following in the commit message:

    This closes #573
    
----
commit 190740f7971be506df5416dc4dfc5714bba0c972
Author: Kenneth Knowles <kl...@google.com>
Date:   2016-07-01T16:53:37Z

    Fix timestamps in GroupAlsoByWindowsProperties
    
    Some of the timestamps were not adjusted when
    BEAM-145 was fixed to respect the WindowFn's
    timestamps.

----


> OutputTimeFn#assignOutputTime overrides WindowFn#getOutputTime in unfortunate ways
> ----------------------------------------------------------------------------------
>
>                 Key: BEAM-145
>                 URL: https://issues.apache.org/jira/browse/BEAM-145
>             Project: Beam
>          Issue Type: Bug
>          Components: runner-core
>            Reporter: Kenneth Knowles
>            Assignee: Kenneth Knowles
>            Priority: Minor
>              Labels: windowing
>             Fix For: 0.1.0-incubating
>
>
> Today the {{OutputTimeFn}} includes {{#assignOutputTime}}, {{#combine}}, and {{#merge}}. Together these express the grouping of timestamps, analogous to the grouping of values in a GBK / Combine, in a canonical way.
> The default {{OutputTimeFn}} is provided by the {{WindowFn}}. In particular, {{SlidingWindows}} provides an {{OutputTimeFn}} that shifts input timestamps later to avoid watermark stuckness and then takes the minimum to compute the output timestamp.
> The SDK additionally provides instance for "min", "max" and "end of window" output timestamps.
> Unfortunately,  if one overrides the {{OutputTimeFn}} to one of these, the shifting done by {{SlidingWindows}} is lost.
> This is actually only a minor problem for now, since "min" is the default, "end of window" is unaffected, and "max" has only esoteric uses.The fix is easy:
> This is interrelated with another suggested change:  Since there are only three common {{OutputTimeFn}} instances, and it is a high bandwidth API, it does not seem worthwhile to leave it in userland. So it is proposed to reduce it to an enum, which would leave only the {{WindowFn}} as a userland place for timestamp adjustments. (requiring special casing for end-of-window, since it cannot be implemented without owning {{#assignOutputTime}})



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