Hi Soheil, Did you read the documentation about Flink Window/Trigger [1]?
FIRE_AND_PURGE usually used to implement the count window. Flink provide a PurgingTrigger as a warper for other trigger to make those triggers can be purge. One of this class use case is count window[2][3]. About your example, you mean the window will triggered by count and time? if it is triggered by count condition we could use FIRE_AND_PURGE. [1]: https://ci.apache.org/projects/flink/flink-docs-release-1.5/dev/stream/operators/windows.html#fire-and-purge [2]: https://github.com/apache/flink/blob/master/flink-streaming-java/src/main/java/org/apache/flink/streaming/api/datastream/DataStream.java#L765 [3]: https://github.com/apache/flink/blob/master/flink-streaming-java/src/main/java/org/apache/flink/streaming/api/datastream/KeyedStream.java#L628 Thanks, vino. 2018-07-17 22:44 GMT+08:00 Soheil Pourbafrani <soheil.i...@gmail.com>: > Hi, > > Can someone elaborate on when the clear method on class Trigger will be > called and what is the duty of that? Also, I don't know what is the benefit > of FIRE_AND_PURGE against FIRE and it's use case. > > For example, in a scenario, if we have a count of 3 Window that also will > trigger after a timeout if we FIRE window on timeout and after a while, a > new data will be added to the data, will window be triggered for all data > or not just for new late data? I guess in such such case we should use the > FIRE_AND_PURGE. > >
