[jira] [Commented] (FLINK-5386) Refactoring Window Clause

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

    [ https://issues.apache.org/jira/browse/FLINK-5386?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15812507#comment-15812507 ] 

ASF GitHub Bot commented on FLINK-5386:
---------------------------------------

Github user shaoxuan-wang commented on a diff in the pull request:

    https://github.com/apache/flink/pull/3046#discussion_r95219196
  
    --- Diff: flink-libraries/flink-table/src/main/scala/org/apache/flink/table/api/table.scala ---
    @@ -785,13 +793,19 @@ class Table(
         * will be processed by a single operator.
         *
         * @param groupWindow group-window that specifies how elements are grouped.
    -    * @return A windowed table.
         */
    -  def window(groupWindow: GroupWindow): GroupWindowedTable = {
    +  def window(groupWindow: GroupWindow): Table = {
         if (tableEnv.isInstanceOf[BatchTableEnvironment]) {
           throw new ValidationException(s"Windows on batch tables are currently not supported.")
         }
    -    new GroupWindowedTable(this, Seq(), groupWindow)
    +    if (None == groupWindow.name) {
    +      throw new ValidationException("An alias must be specified for the window.")
    +    }
    +    if (windowPool.contains(groupWindow.name.get)) {
    +      throw new ValidationException("The window alias can not be duplicated.")
    --- End diff --
    
    s/"The window alias can not be duplicated."/"The same window alias has been defined"/


> 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: 
> 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)
> 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:
>   .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)
> What do you think? [~fhueske] [~twalthr]



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