Made a mistake on the example above, and update it as follows:
// Table function windowing syntax.
SELECT
product_id, count(*), window_start
FROM TABLE(TUMBLE(order, DESCRIPTOR(rowtime), INTERVAL '1' hour))
GROUP BY product_id, window_start
On Wed, Apr 22, 2020 at 2:31 PM Rui Wang <amaliu...@apache.org> wrote:
> Hi community,
>
> I want to kick off a discussion about deprecating grouped window functions
> (GROUP BY TUMBLE/HOP/SESSION) as the table function windowing support
> becomes a thing [1] (FROM TABLE(TUMBLE/HOP/SESSION)). The current stage of
> table function windowing is TUMBLE support is checked in. HOP and SESSION
> support is likely to be merged in 1.23.0.
>
> A briefly example of two different windowing syntax:
>
> // Grouped window functions.
> SELECT
> product_id, count(*), TUMBLE_START() as window_start
> FROM order
> GROUP BY product_id, TUMBLE(rowtime, INTERVAL '1' hour); // an hour long
> fixed window size.
>
> // Table function windowing syntax.
> SELECT
> product_id, count(*), window_start
> FROM TABLE(TUMBLE(order, DESCRIPTOR(.rowtime), INTERVAL '1' hour)
> GROUP BY product_id
>
> I am giving a short, selective comparison as the following:
>
> The places that table function windowing behaves better
> 1) no GROUPING/GROUP BY enforced. It becomes a problem in streaming JOIN.
> For example, one use case is for each hour, apply a JOIN on two streams. In
> this case, no GROUP BY is needed.
> 2) grouped window functions allow multiple calls in GROUP BY. For example,
> from SQL syntax perspective, GROUP BY TUMBLE(...), HOP(...), SESSION(...)
> is not wrong, but it is an illegal query.
> 3) Calcite includes an Enumerable implementation of table function
> windowing, while grouped window functions do not have that.
>
>
> The places that table function windowing behaves worse
> 1) table function windowing adds "window_start", "window_end" into table
> directly, which increases the volume of data (number of rows *
> sizeof(timestamp) * 2).
>
>
> I want to focus on discussing two questions in this thread:
> 1) Do people support deprecating grouped window functions?
> 2) By which version people prefer to make grouped window functions
> completely removed?(if 1) is yes).
>
>
>
> [1]: https://jira.apache.org/jira/browse/CALCITE-3271
>
>
> -Rui
>
