{"record":{"id":"9ea7685c34e8a04d","repo":"apache/flink","slug":"reduce-hint-must-not-be-null","errorCode":null,"errorMessage":"Reduce Hint must not be null.","messagePattern":"Reduce Hint must not be null\\.","errorType":"validation","errorClass":"IllegalArgumentException","httpStatus":null,"severity":"error","filePath":"flink-core/src/main/java/org/apache/flink/api/common/operators/base/ReduceOperatorBase.java","lineNumber":279,"sourceCode":"        } else {\n            T aggregate = inputData.get(0);\n\n            aggregate = serializer.copy(aggregate);\n\n            for (int i = 1; i < inputData.size(); i++) {\n                T next = function.reduce(aggregate, serializer.copy(inputData.get(i)));\n                aggregate = serializer.copy(next);\n            }\n\n            FunctionUtils.setFunctionRuntimeContext(function, ctx);\n\n            return Collections.singletonList(aggregate);\n        }\n    }\n\n    public void setCombineHint(CombineHint hint) {\n        if (hint == null) {\n            throw new IllegalArgumentException(\"Reduce Hint must not be null.\");\n        }\n        this.hint = hint;\n    }\n\n    public CombineHint getCombineHint() {\n        return hint;\n    }\n}\n","sourceCodeStart":261,"sourceCodeEnd":288,"githubUrl":"https://github.com/apache/flink/blob/2f3c205e9266cb30240eb7f4fdab15cad629a70f/flink-core/src/main/java/org/apache/flink/api/common/operators/base/ReduceOperatorBase.java#L261-L288","documentation":"Error \"Reduce Hint must not be null.\" thrown in apache/flink.","triggerScenarios":"Triggered at runtime when the operation fails because: Reduce Hint must not be null.","commonSituations":"Commonly caused by misconfiguration, missing dependencies or files, unsupported types or operations, or invalid user input leading to: Reduce Hint must not be null.","solutions":["Address the cause reported by the error message: Reduce Hint must not be null.","Verify the inputs, configuration values, and classpath/dependency setup related to this operation, then retry."],"exampleFix":"Correct the condition described (\"Reduce Hint must not be null.\") and rerun the job or command.","handlingStrategy":null,"validationCode":null,"typeGuard":null,"tryCatchPattern":null,"preventionTips":[],"tags":[],"backgroundTag":null,"analyzedSha":"2f3c205e9266cb30240eb7f4fdab15cad629a70f","analyzedAt":"2026-08-14T08:48:24.518Z","schemaVersion":2},"datasetVersion":"2026-08-14T10:17:34.591Z"}