[FLINK-2135] Java plan translation fails with ClassCastException (probably in first())

• Type: Bug
• Status: Resolved
• Priority: Major
• Resolution: Fixed
• Affects Version/s: 0.9
• Fix Version/s: 0.9
• Assignee: Robert Metzger
• Reporter: Robert Metzger
• Created: 02/Jun/15 15:46
• Updated: 28/Feb/19 14:29
• Resolved: 04/Jun/15 11:17

Description

A user reported the following error

Exception in thread "main" java.lang.ClassCastException: org.apache.flink.api.java.functions.FirstReducer cannot be cast to org.apache.flink.api.common.functions.RichGroupReduceFunction
	at org.apache.flink.api.java.operators.translation.PlanUnwrappingSortedReduceGroupOperator.<init>(PlanUnwrappingSortedReduceGroupOperator.java:40)
	at org.apache.flink.api.java.operators.GroupReduceOperator.translateSelectorFunctionSortedReducer(GroupReduceOperator.java:278)
	at org.apache.flink.api.java.operators.GroupReduceOperator.translateToDataFlow(GroupReduceOperator.java:177)
	at org.apache.flink.api.java.operators.GroupReduceOperator.translateToDataFlow(GroupReduceOperator.java:50)
	at org.apache.flink.api.java.operators.OperatorTranslation.translateSingleInputOperator(OperatorTranslation.java:124)
	at org.apache.flink.api.java.operators.OperatorTranslation.translate(OperatorTranslation.java:86)
	at org.apache.flink.api.java.operators.OperatorTranslation.translateSingleInputOperator(OperatorTranslation.java:122)
	at org.apache.flink.api.java.operators.OperatorTranslation.translate(OperatorTranslation.java:86)
	at org.apache.flink.api.java.operators.OperatorTranslation.translateSingleInputOperator(OperatorTranslation.java:122)
	at org.apache.flink.api.java.operators.OperatorTranslation.translate(OperatorTranslation.java:86)
	at org.apache.flink.api.java.operators.OperatorTranslation.translate(OperatorTranslation.java:61)
	at org.apache.flink.api.java.operators.OperatorTranslation.translateToPlan(OperatorTranslation.java:49)
	at org.apache.flink.api.java.ExecutionEnvironment.createProgramPlan(ExecutionEnvironment.java:925)
	at org.apache.flink.api.java.ExecutionEnvironment.createProgramPlan(ExecutionEnvironment.java:893)
	at org.apache.flink.api.java.LocalEnvironment.execute(LocalEnvironment.java:50)
	at org.apache.flink.api.java.ExecutionEnvironment.execute(ExecutionEnvironment.java:789)
	at org.apache.flink.api.java.DataSet.collect(DataSet.java:411)
	at org.apache.flink.api.java.DataSet.print(DataSet.java:1346)
	at com.dataartisans.GroupReduceBug.main(GroupReduceBug.java:43)
	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
	at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
	at java.lang.reflect.Method.invoke(Method.java:606)
	at com.intellij.rt.execution.application.AppMain.main(AppMain.java:140)

It is reproducible with the following code

		ExecutionEnvironment ee = ExecutionEnvironment.getExecutionEnvironment();

		DataSet<String> b = ee.fromElements("a", "b");
		GroupReduceOperator<String, String> a = b.groupBy(new KeySelector<String, Long>() {
			@Override
			public Long getKey(String value) throws Exception {
				return 1L;
			}
		}).sortGroup(new KeySelector<String, Double>() {
			@Override
			public Double getKey(String value) throws Exception {
				return 1.0;
			}
		}, Order.DESCENDING).first(10);

		a.print();