...

The existing Grouped window functions, i.e. GROUP BY TUMBLE... are still supported, but will be deprecated. We can drop the old syntax at some point in the future, but this needs another public discussion. We should update the examples, docs to only use the new one. The support for Table API is a future work and should be in a separate FLIP.

Future Work

Simplify Polymorphic Table Functions syntax

As disucssed in the mailing list, the current PTF syntax is verbose, it would be great if we can remove TABLE() keyword, that would be easier to be picked up by users. Oracle and SQL Server both don't need such keywords. A simplified query would be like this:

SELECT *
FROM TUMBLE(inputTable, DESCRIPTOR(timecol), INTERVAL '10' MINUTE);

Support count window with the window TVF

...

SELECT *
FROM TABLE(
   TUMBLE_ROW(
     data => TABLE inputTable,
     timecol => DESCRIPTOR(timecol),
     size => 10));

Explore more ability of Polymorphic Table Functions

It's very exciting to see the potential ability of PTF.  As we can see, in the future, maybe we can support the following features in SQL in a standard PTF way.

• advanced operations supported in Table API (FLIP-29), e.g. drop_columns, user-defined-table-aggregate
• user defined join operator
• a shortcut TopN function
• re-assign watermarks?
• re-partition data, similar feature to Hive DISTRIBUTED BY syntax. 
• ...