前言
通常我们在需要输出Table表数据时需要转换成DataStream流进行输出,然后转换流有两种模式toAppendStream追加模式、toRetractStream更新模式
toAppendStream:追加模式
- 接收端口数据,测试追加模式
代码示例
import org.apache.flink.streaming.api.scala._
import org.apache.flink.table.api.{
EnvironmentSettings, Table}
import org.apache.flink.table.api.scala._
//定义样例类WaterSensor
case class WaterSensor(id:String,ts:Long,vc:Double)
object TableOutCsv {
def main(args: Array[String]): Unit = {
//创建流执行环境
val env: StreamExecutionEnvironment = StreamExecutionEnvironment.getExecutionEnvironment
//创建表执行环境
val table: EnvironmentSettings = EnvironmentSettings.newInstance()
.useBlinkPlanner()
.inStreamingMode()
.build()
val tableEnv: StreamTableEnvironment = StreamTableEnvironment.create(env,table)
//接收指定端口得数据,并转换成样例类WaterSensor类型的DataStream
val dataStream: DataStream[WaterSensor] = env.socketTextStream("192.168.95.99",7777)
.map(a=>{
val strings: Array[String] = a.split(",")
WaterSensor(strings(0),strings(1).toLong,strings(2).toDouble)
})
//根据流创建一张Table类型得得对象
val dataTable: Table = tableEnv.fromDataStream(dataStream)
//调用Table API进行转换
val dataTable2: Table = dataTable.select("id,vc").filter('id === "ws_003")
//使用追加模式,当有数据更新时,直接在后面跟着输出
dataTable2.toAppendStream[(String,Double)].print("append")
//启动执行
env.execute()
}
}
启动端口
启动程序
测试数据
ws_001,1577844001,24.0
ws_002,1577844015,43.0
ws_003,1577844020,32.0
端口输入
程序输出
追加数据
ws_003,1577844020,23.0
ws_003,1577844020,65.0
程序输出
结论:使用toAppendStream就是当接收到新得数据时候不会影响之前得数据,而是在后面追加
toRetractStream:更新模式
- 依然是接收端口数据,只不过这次我们使用Table API对数据进行count,查看使用toRetractStream得效果
代码示例
import org.apache.flink.streaming.api.scala._
import org.apache.flink.table.api.{
EnvironmentSettings, Table}
import org.apache.flink.table.api.scala._
//定义样例类WaterSensor
case class WaterSensor(id:String,ts:Long,vc:Double)
object TableOutCsv {
def main(args: Array[String]): Unit = {
//创建流执行环境
val env: StreamExecutionEnvironment = StreamExecutionEnvironment.getExecutionEnvironment
//创建表执行环境
val table: EnvironmentSettings = EnvironmentSettings.newInstance()
.useBlinkPlanner()
.inStreamingMode()
.build()
val tableEnv: StreamTableEnvironment = StreamTableEnvironment.create(env,table)
//接收指定端口得数据,并转换成样例类WaterSensor类型的DataStream
val dataStream: DataStream[WaterSensor] = env.socketTextStream("192.168.95.99",7777)
.map(a=>{
val strings: Array[String] = a.split(",")
WaterSensor(strings(0),strings(1).toLong,strings(2).toDouble)
})
//根据流创建一张Table类型得得对象
val dataTable: Table = tableEnv.fromDataStream(dataStream)
//调用Table API进行转换
val dataTable2: Table = dataTable
.groupBy('id) //根据ID进行分组
.select('id,'vc.count as 'countVC) //count相同ID得vc值
//使用追加模式,当有数据更新时,直接在后面跟着输出
dataTable2.toRetractStream[(String,Double)].print("retract")
//启动执行
env.execute()
}
}
启动端口
启动程序
测试数据
ws_001,1577844001,24.0
ws_002,1577844015,43.0
ws_003,1577844020,32.0
端口输入
程序输出
追加数据
ws_003,1577844020,23.0
ws_003,1577844020,65.0
程序输出
结论:从输出得结果看,每条结果前都会有true,当接收到新得数据时会更新原先得数据,并在原先得数据前面标记false,也就是失效或者作废得意思,从而得到新得数据,到此应该也能很清晰得区分 toAppendStream与toRetractStream的区别了把