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https://issues.apache.org/jira/browse/FLINK-40289?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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ASF GitHub Bot updated FLINK-40289:
-----------------------------------
Labels: pull-request-available (was: )
> Window Top-N examples are not reproducible in streaming mode
> ------------------------------------------------------------
>
> Key: FLINK-40289
> URL: https://issues.apache.org/jira/browse/FLINK-40289
> Project: Flink
> Issue Type: Improvement
> Components: Documentation, Table SQL / API
> Affects Versions: 2.3.0
> Reporter: Hancheng Deng
> Priority: Major
> Labels: pull-request-available
>
> h2. Description
> The Window Top-N documentation shows six output rows for two 10-minute
> tumbling windows while defining the following watermark:
> {code:sql}
> WATERMARK FOR bidtime AS bidtime - INTERVAL '1' SECOND
> {code}
> However, the maximum event time in the displayed input is {{2020-04-15
> 08:17:00.000}}. Therefore, in streaming mode, the watermark can advance only
> to approximately {{2020-04-15 08:16:59.000}}.
> This closes the {{[08:00, 08:10)}} window, but does not close the {{[08:10,
> 08:20)}} window. With an unbounded streaming source and only the displayed
> records, only the first three output rows can be reproduced. The three rows
> shown for the second window are not emitted until later records advance the
> watermark past the window end.
> The six displayed rows are valid as final results for bounded/batch input, or
> when subsequent streaming records advance the watermark sufficiently. Neither
> condition is explained in the example.
> This issue is present in the Flink 1.20 LTS documentation, the Flink 2.3
> stable documentation, and the current documentation source.
> h2. Affected documentation
> * [Flink 1.20 Window
> Top-N|https://nightlies.apache.org/flink/flink-docs-release-1.20/docs/dev/table/sql/queries/window-topn/]
> * [Flink 2.3 Window
> Top-N|https://nightlies.apache.org/flink/flink-docs-release-2.3/docs/sql/reference/queries/window-topn/]
> * {{docs/content/docs/sql/reference/queries/window-topn.md}}
> * {{docs/content.zh/docs/sql/reference/queries/window-topn.md}}
> h2. Steps to reproduce
> # Use an unbounded streaming source containing only the nine records
> displayed in the documentation.
> # Define {{WATERMARK FOR bidtime AS bidtime - INTERVAL '1' SECOND}}.
> # Run the documented Window Top-N query.
> # Observe that only the Top 3 rows for {{[08:00, 08:10)}} are emitted.
> # No rows for {{[08:10, 08:20)}} are emitted because the watermark never
> reaches the end of that window.
> h2. Expected documentation improvement
> Clarify that the displayed tables represent final results after both windows
> have closed:
> * In batch mode, bounded input completion closes the remaining windows.
> * In streaming mode, subsequent events must advance the watermark past the
> window end before Window Top-N emits the final result.
> * With only the displayed records in an unbounded source, only the first
> window result is emitted.
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