Hello, The result contains (a,Map(3 -> rt)) because reduce prints all intermediate results (sometimes called a "rolling reduce"). It's designed this way, because Flink streams are generally infinite, so there is no last element where you could print the "final" results. However, you can use windowing [1] to perform the reduce on elements that arrived in certain time intervals called windows, in which case only the final results for a window are emitted.
Best, Gábor [1] https://ci.apache.org/projects/flink/flink-docs-release-1.1/apis/streaming/windows.html 2016-08-29 11:08 GMT+02:00 <rimin...@sina.cn>: > Hi, > in flink,the datastream have reduce Transformations,but the result do > not satisfy for me, > for example, > val pairs2 = env.fromCollection((Array(("a", Map(3->"rt")),("a", > Map(4->"yt")),("b", Map(5->"dfs"))))) > val re= pairs2.keyBy(0).reduce((x1,x2)=>(x1._1,x2._2++x1._2)) > re.map{x=> > println(x) > x > } > > the result are, > (a,Map(3 -> rt)) > (a,Map(3 -> rt, 4 -> yt)) > (b,Map(5 -> dfs)) > > but i want to get , > (a,Map(3 -> rt, 4 -> yt)) > (b,Map(5 -> dfs)) > > -------------------------------- > >
