[jira] [Created] (FLINK-22455) FlinkRelBuilder#windowAggregate will throw ClassCastException when function reuse

[Shang Yuanchun (Jira)]

tartarus created FLINK-22455:
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             Summary: FlinkRelBuilder#windowAggregate will throw ClassCastException when function reuse
                 Key: FLINK-22455
                 URL: https://issues.apache.org/jira/browse/FLINK-22455
             Project: Flink
          Issue Type: Bug
          Components: Table SQL / Planner
            Reporter: tartarus
         Attachments: FlinkRelBuilderTest.scala

If the input parameter aggCalls of FlinkRelBuilder#windowAggregate contains the same aggregate function. Then it will throw ClassCastException, because of the optimization of aggregate function reuse. We did not judge the return value type, but direct type conversion;
{code:java}
    val aggregate = super.transform(
      new UnaryOperator[RelBuilder.Config] {
        override def apply(t: RelBuilder.Config)
          : RelBuilder.Config = t.withPruneInputOfAggregate(false)
      })
      .push(build())
      .aggregate(groupKey, aggCalls)
      .build()
      .asInstanceOf[LogicalAggregate]
{code}
I wrote a test that triggered this problem.
You can use the attached code to reproduce this problem.




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