Details
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Bug
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Status: Resolved
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Major
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Resolution: Fixed
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0.9
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None
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None
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();