[GitHub] flink issue #3252: [FLINK-5624] Support tumbling window on streaming tables ...

[fhueske <gi...@git.apache.org>]

Github user fhueske commented on the issue:

    https://github.com/apache/flink/pull/3252
  
    Hi @haohui, thanks for your contribution!
    
    The referenced JIRA is about adding support for group windows to SQL, not OVER (or row) windows. It should enable queries such as:
    
    ```
    SELECT a, sum(b) as sumB, TUMBLE_END(rowtime(), INTERVAL '1' HOUR) AS t,
      FROM myT
    GROUP BY TUMBLE(rowtime(), INTERVAL '1' HOUR), a;
    ```
    
    I saw that you contributed `TUMBLE` just very recently to Calcite, so this feature is not yet available in a Calcite release that we could link against. Until then, we could add support for the more manual version of SQL tumbling windows:
    
    ```
    SELECT a, SUM(b) AS sumB, CEIL(rowtime() TO HOUR) AS t,
      FROM myT
    GROUP BY CEIL(rowtime() TO HOUR), a
    ```
    
    We would also need to find a way to reference the `rowtime`. We do not want to expose this as an actual attribute in Flink's SQL (internally, Flink treats record timestamps as metadata which may not be modified by a query). The current approach would be to implement a built-in function which serves as a marker and is replaced during the translation.
    
    Best, Fabian


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