Flink window Function– window concept

Window division:

1. Tumbling window (Tumbling Window, no overlap)
2. Scroll window (Sliding Window, overlapping)
3. Session window (Session Window, space activity)

Window Type:

   Window before processing the data, the data will have to do triage, there are two ways to control flow, according to the data stream is divided: Keyed and Non-Keyed Windows.

   Keyed Windows: is there a window in accordance with the packet data stream a field of use, can be understood as classified according to the original data stream of a key, the data stream has the same key value will be into the same window, multiple windows parallel logic flow.

   Non-Keyed Windows: no window to use a field in accordance with data packets

Window operator:

   Calculated based on the window data, called a window function. Support four:

   1. Low ProcessWindowFunction efficiency, the entire window of data will be transmitted to the operator, see Code: Flink window Function - ProcessWindowFunction

   2. ReduceFunction easy to use, recommended, Refer to code: Flink window Function - ReduceWordCount

   3. AggregateFunction complex logic, see the code: Flink window Function - the AggregateFunction

   4. FoldFunction outdated API, is not friendly enough, Refer to code: Flink window Function - FoldFunction