[FLINK-11456] Improve window operator with sliding window assigners

• Type: Improvement
• Status: Closed
• Priority: Major
• Resolution: Invalid
• Component/s: API / DataStream
• Assignee: vinoyang
• Reporter: Rong Rong
• Created: 29/Jan/19 15:31
• Updated: 19/Sep/19 19:16
• Resolved: 02/Mar/19 17:49

Description

With Slicing and merging operators that exposes the internals of window operators. current sliding window can be improved by eliminating duplicate aggregations or duplicate element insert into multiple panes (e.g. namespaces). 

The following sliding window operation

val resultStream: DataStream = inputStream
  .keyBy("key")
  .window(SlidingEventTimeWindow.of(Time.seconds(5L), Time.seconds(15L)))
  .sum("value")

can produce job graph equivalent to

val resultStream: DataStream = inputStream
  .keyBy("key")
  .sliceWindow(Time.seconds(5L))
  .sum("value")
  .slideOver(Count.of(3))