How to get only the last aggregated value for a window?

Question

I would like to aggregate a Kafka topic with a tumbling window and get only the last aggregated value for each window.

With the code, pasted below, the aggregated value is updated each time a new event arrives. So I get as many aggregated values as number of incoming events. I would like to have a topic with only last aggregated value for each window. Is it possible to achieve that (with ksqldb)?

CREATE TABLE all_pieces_tumbling AS
SELECT ResourceID, SUM(Value)
FROM all_pieces_stream
WINDOW TUMBLING (SIZE 1 MINUTE)
WHERE EventType = 23
GROUP BY ResourceID;

user_4953079 · Answer

You can use EMIT FINAL instead of EMIT CHANGES to only get the "final result".

Be aware about the "data driven" nature of EMIT FINAL though: KSQLDB Emit Final does not return any value

How to get only the last aggregated value for a window?

1 Answers