Hi Weizheng, You are right. You can use the TopN feature in blink planner. But note that it doesn't support tumbling window topn, it is a topn without windowing and event-time. But you can achieve it by PARTITIONED BY <time-window>, the <time-window> column could be a preprocessed column which represents which window does this row belongs to, e.g. 1-hour windowing: "2020-03-02 10:00", "2020-03-02 11:00".
The tumbling window topn will be natively supported in the future. Best, Jark On Mon, 2 Mar 2020 at 10:55, Lu Weizheng <luweizhen...@hotmail.com> wrote: > Sorry guys, > > I find solution on wiki about Top-N using Blink planner. > > SELECT [column_list]FROM ( > SELECT [column_list], > ROW_NUMBER() OVER ([PARTITION BY col1[, col2...]] > ORDER BY col1 [asc|desc][, col2 [asc|desc]...]) AS rownum > FROM table_name)WHERE rownum <= N [AND conditions] > > > thanks anyway. > ------------------------------ > *发件人:* Lu Weizheng <luweizhen...@hotmail.com> > *发送时间:* 2020年3月1日 17:48 > *收件人:* user@flink.apache.org <user@flink.apache.org> > *主题:* Get Tumbling Window Top-K using SQL > > Hi, > > I find a question on StackOverflow( > https://stackoverflow.com/questions/49191326/flink-stream-sql-order-by) > about how to get Top-K using Flink SQL, it was written by Fabian. It was > backed in 2018. > The main idea is using a RANK to get the Top K of filed 'a'： > > SELECT a, b, c > FROM ( > SELECT > a, b, c, > RANK() OVER (ORDER BY a PARTITION BY CEIL(t TO MINUTE) BETWEEN UNBOUNDED > PRECEDING AND CURRENT ROW) as rank > FROM yourTable) > WHERE rank <= 10 > > is there better way to get tumbling window Top-K item now? > > And the wiki on dynamic table may need to update. > https://ci.apache.org/projects/flink/flink-docs-release-1.10/dev/table/streaming/dynamic_tables.html > > In the above wiki, I don't know why the query has a field 'lastLogin' > > SELECT user, RANK() OVER (ORDER BY lastLogin)FROM ( > SELECT user, MAX(cTime) AS lastAction FROM clicks GROUP BY user); > > > Thanks! >
