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https://issues.apache.org/jira/browse/FLINK-5386?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15814699#comment-15814699
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Fabian Hueske commented on FLINK-5386:
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Hi, sorry for the delayed reply.
I like the idea of making the use of group and row windows consistent. Also
referencing the window alias in {{groupBy}} is OK for me.
However, I am not so sure about the proposal to define windows anywhere in the
Table API query as in the example above where {{w1}} and {{w2}} are defined at
the start and used later.
For batch tables, windows can be defined on arbitrary time attributes (e.g.,
{{orderTime}}). It might happen that we define a window on a time attribute,
perform some other operations which removed the window time attribute, and try
to groupBy the defined window, however, the window attribute is no longer
present in the input.
Of course we can validate that the attribute exists and give a meaningful error
message. However, by tying {{window}} and {{groupBy}} together, we could avoid
such situations.
What do you think?
> Refactoring Window Clause
> -------------------------
>
> Key: FLINK-5386
> URL: https://issues.apache.org/jira/browse/FLINK-5386
> Project: Flink
> Issue Type: Sub-task
> Components: Table API & SQL
> Reporter: sunjincheng
> Assignee: sunjincheng
>
> Similar to the SQL, window clause is defined "as" a symbol which is
> explicitly used in groupby/over. We are proposing to refactor the way to
> write groupby+window tableAPI as follows:
> {code}
> val windowedTable = table
> .window(Slide over 10.milli every 5.milli as 'w1)
> .window(Tumble over 5.milli as 'w2)
> .groupBy('w1, 'key)
> .select('string, 'int.count as 'count, 'w1.start)
> .groupBy( 'w2, 'key)
> .select('string, 'count.sum as sum2)
> .window(Tumble over 5.milli as 'w3)
> .groupBy( 'w3) // windowAll
> .select('sum2, 'w3.start, 'w3.end)
> {code}
> In this way, we can remove both GroupWindowedTable and the window() method in
> GroupedTable which makes the API a bit clean. In addition, for row-window, we
> anyway need to define window clause as a symbol. This change will make the
> API of window and row-window consistent, example for row-window:
> {code}
> .window(RowXXXWindow as ‘x, RowYYYWindow as ‘y)
> .select(‘a, ‘b.count over ‘x as ‘xcnt, ‘c.count over ‘y as ‘ycnt, ‘x.start,
> ‘x.end)
> {code}
> What do you think? [~fhueske] [~twalthr]
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