我正在实现一个sourcefunction，它从数据库中读取数据。如果停止或压碎（即保存点和检查点），作业应该能够恢复，数据只处理一次。
到目前为止我所拥有的：

@SerialVersionUID(1L)
class JDBCSource(private val waitTimeMs: Long) extends 
RichParallelSourceFunction[Event] with StoppableFunction with LazyLogging{

    @transient var client: PostGreClient = _
    @volatile var isRunning: Boolean = true
    val DEFAULT_WAIT_TIME_MS = 1000

    def this(clientConfig: Serializable) =
        this(clientConfig, DEFAULT_WAIT_TIME_MS)

    override def stop(): Unit = {
        this.isRunning = false
    }

    override def open(parameters: Configuration): Unit = {
        super.open(parameters)
        client = new JDBCClient
    }

    override def run(ctx: SourceFunction.SourceContext[Event]): Unit = {

        while (isRunning){
           val statement = client.getConnection.createStatement()
           val resultSet = statement.executeQuery("SELECT name, timestamp FROM MYTABLE")

            while (resultSet.next()) {
                val event: String = resultSet.getString("name")
                val timestamp: Long = resultSet.getLong("timestamp")

                ctx.collectWithTimestamp(new Event(name, timestamp), timestamp)

            }
        }
    }

    override def cancel(): Unit = {
        isRunning = false
    }
}

如何确保只获取数据库中尚未处理的行？我以为 ctx 变量将包含一些有关当前水印的信息，以便我可以将查询更改为以下内容：

select name, timestamp from myTable where timestamp > ctx.getCurrentWaterMark

但对我来说没有任何相关的方法。任何解决这个问题的办法都将不胜感激