按进程时间窗口分组不会产生任何结果

如果我运行下面的select,则不会产生任何结果

 SELECT
       TUMBLE_START(pt, INTERVAL '4' second),
       sum(price)
   FROM sourceTable
   GROUP BY TUMBLE(pt, INTERVAL '4' second)

如果我运行下面的select,那么结果是正确的。

tenv.sqlQuery("select key, price, pt from sourceTable").toAppendStream[Row].print()

有人能帮忙看看吗?

package org.example.sql4

import org.apache.flink.streaming.api.scala._
import org.apache.flink.table.api.TableResult
import org.apache.flink.table.api.bridge.scala._
import org.apache.flink.types.Row

object Sql017_ProcessTimeAttributeDDLTest {
  def main(args: Array[String]): Unit = {
    val env = StreamExecutionEnvironment.getExecutionEnvironment
    env.setParallelism(1)
    val tenv = StreamTableEnvironment.create(env)

    val ddl =
      """
      create table sourceTable(
      key STRING,
      `date` STRING, ---date is a key word
      price DOUBLE,
      pt as PROCTIME() ---processing time
      ) with (
        'connector' = 'filesystem',
        'path' = 'd:/stock.csv',
        'format' = 'csv'
      )
      """.stripMargin(' ')
    val result: TableResult = tenv.executeSql(ddl)
    result.print()

//   The following query produces correct result
//    tenv.sqlQuery("select key, price, pt from sourceTable").toAppendStream[Row].print()

    val sql =
      """
       SELECT
           TUMBLE_START(pt, INTERVAL '4' second),
           sum(price)
       FROM sourceTable
       GROUP BY TUMBLE(pt, INTERVAL '4' second)
     """.stripMargin(' ')

    //this query doesn't produce any result
    tenv.sqlQuery(sql).toAppendStream[Row].print()

    env.execute()

    Thread.sleep(20000)
  }

}

这个股票.csv是:

key1,2020-09-16 20:50:15,1
key1,2020-09-16 20:50:12,2
key1,2020-09-16 20:50:11,3
key1,2020-09-16 20:50:18,4
key1,2020-09-16 20:50:13,5
key1,2020-09-16 20:50:20,6
key1,2020-09-16 20:50:14,7
key1,2020-09-16 20:50:22,8
key1,2020-09-16 20:50:40,9