详解 Flink Table API 和 Flink SQL 之窗口操作

时间语义，要配合窗口操作才能发挥作用

一、Group Window

分组窗口（Group Windows）会根据时间或行计数间隔，将行聚合到有限的组（Group）中，并对每个组的数据执行一次聚合函数。主要分为滚动窗口、滑动窗口和会话窗口

public class TestGroupWindow {
   
    public static void main(String[] args) throws Exception {
   
        StreamExecutionEnvironment env = StreamExecutionEnvironment.getExecutionEnvironment();
        env.setParallelism(1);
        //开启事件时间语义
        env.setStreamTimeCharacteristic(TimeCharacteristic.EventTime);
        
        StreamTableEnvironment tableEnv = StreamTableEnvironment.create(env);
        
        DataStream<String> inputStream = env.readTextFile("./sensor.txt");
        DataStream<SensorReading> dataStream = inputStream.map(line -> {
   
            String[] fields = line.split(",");
            return new SensorReading(fields[0], new Long(fields[1]), new Double(fields[2]));
        })
            //提取事件时间戳和设置watermark