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Posted to dev@flink.apache.org by "Andrew Roberts (JIRA)" <ji...@apache.org> on 2018/08/18 01:54:00 UTC
[jira] [Created] (FLINK-10167) SessionWindows not compatible with
typed DataStreams in scala
Andrew Roberts created FLINK-10167:
--------------------------------------
Summary: SessionWindows not compatible with typed DataStreams in scala
Key: FLINK-10167
URL: https://issues.apache.org/jira/browse/FLINK-10167
Project: Flink
Issue Type: Bug
Reporter: Andrew Roberts
I'm trying to construct a trivial job that uses session windows, and it looks like the data type parameter is hardcoded to `Object`/`AnyRef`. Due to the invariance of java classes in scala, this means that we can't use the provided SessionWindow helper classes in scala on typed streams.
Example job:
{code:java}
import org.apache.flink.api.scala._
import org.apache.flink.streaming.api.scala.{DataStream, StreamExecutionEnvironment}
import org.apache.flink.streaming.api.windowing.assigners.ProcessingTimeSessionWindows
import org.apache.flink.streaming.api.windowing.time.Time
import org.apache.flink.streaming.api.windowing.windows.{TimeWindow, Window}
import org.apache.flink.util.Collector
object TestJob {
val jobName = "TestJob"
def main(args: Array[String]): Unit = {
val env = StreamExecutionEnvironment.getExecutionEnvironment
env.fromCollection(Range(0, 100).toList)
.keyBy(_ / 10)
.window(ProcessingTimeSessionWindows.withGap(Time.minutes(1)))
.reduce(
(a: Int, b: Int) => a + b,
(key: Int, window: Window, items: Iterable[Int], out: Collector[String]) => s"${key}: ${items}"
)
.map(println(_))
env.execute(jobName)
}
}{code}
Compile error:
{code:java}
[error] found : org.apache.flink.streaming.api.windowing.assigners.ProcessingTimeSessionWindows
[error] required: org.apache.flink.streaming.api.windowing.assigners.WindowAssigner[_ >: Int, ?]
[error] Note: Object <: Any (and org.apache.flink.streaming.api.windowing.assigners.ProcessingTimeSessionWindows <: org.apache.flink.streaming.api.windowing.assigners.MergingWindowAssigner[Object,org.apache.flink.streaming.api.windowing.windows.TimeWindow]), but Java-defined class WindowAssigner is invariant in type T.
[error] You may wish to investigate a wildcard type such as `_ <: Any`. (SLS 3.2.10)
[error] .window(ProcessingTimeSessionWindows.withGap(Time.minutes(1))){code}
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