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This article introduces the relevant knowledge of "how to use the MaxBy of Flink". In the operation of actual cases, many people will encounter such a dilemma, so let the editor lead you to learn how to deal with these situations. I hope you can read it carefully and be able to achieve something!

MaxBy aggregation: gets the largest record row in a set of data flow operators (unlike max, max is the maximum value that returns a calculated field)

Sample environment

Java.version: 1.8.xflink.version: 1.11.1

Sample data source (project code cloud download)

Building Development Environment and data of Flink system example

MaxBy.java

Import com.flink.examples.DataSource;import org.apache.flink.api.common.typeinfo.Types;import org.apache.flink.api.java.functions.KeySelector;import org.apache.flink.api.java.tuple.Tuple3;import org.apache.flink.streaming.api.datastream.DataStream;import org.apache.flink.streaming.api.environment.StreamExecutionEnvironment;import java.util.List / * * @ Description maxBy aggregation: get the largest row of records in a set of data flow operators (unlike max, max is the maximum value that returns the calculated field) * / public class MaxBy {/ * * traversal collection Returns the maximum age data record for each gender segment * @ param args * @ throws Exception * / public static void main (String [] args) throws Exception {final StreamExecutionEnvironment env = StreamExecutionEnvironment.getExecutionEnvironment () List tuple3List = DataSource.getTuple3ToList () DataStream dataStream = env.fromCollection (tuple3List) .returns (Types.TUPLE (Types.STRING, Types.STRING,Types.INT)) .keyby ((KeySelector) k-> k.f1) / / scroll by quantity window, every 3 input data streams Calculate once. CountWindow (3) / / Note: the calculation variable is f2.maxBy (2) DataStream.print (); env.execute ("flink MaxBy job");}}

Print the result

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