Hi I am not sure if I understand your question correctly, so will try to explain the flow how elements gets into window operators.
Flink makes the partition assignment before invoking the operator to process element. For the word count example, WindowOperator is invoked by StreamInputProcessor[1] to "setKeyContextElement". The actual key is then set by WindowOperator (inherently by AbstractStreamOperator[2]), which ultimately passed to KeyedStateBackend[3]. So, by the time WindowOperator processes elements, the KeyedStateBackend was already set to the correct key. Hope this answers your question. -- Rong [1] https://ci.apache.org/projects/flink/flink-docs-release-1.7/api/java/org/apache/flink/streaming/runtime/io/StreamInputProcessor.html [2] https://ci.apache.org/projects/flink/flink-docs-release-1.7/api/java/org/apache/flink/streaming/api/operators/AbstractStreamOperator.html On Sun, Mar 3, 2019 at 5:15 AM 刘 文 <thinktothi...@yahoo.com> wrote: > ). Environment Flink1.7.2 WordCount local, stream processing > ).source RecordWriter.emit(), for each element by key, divided into > different partitions, the partition location of each element has been > determined, the number of partitions is determined by > DataStream.setParallelism(2) > ). By copyFromSerializerToTargetChannel(int targetChannel) to write data > to different channels, it is to send data to the window corresponding to > different partitions (data is sent one by one)
