{"record":{"id":"5790208ec5902f33","repo":"apache/flink","slug":"a-side-output-with-a-matching-id-was-already-reque","errorCode":null,"errorMessage":"A side output with a matching id was already requested with a different type. This is not allowed, side output ids need to be unique.","messagePattern":"A side output with a matching id was already requested with a different type\\. This is not allowed, side output ids need to be unique\\.","errorType":"validation","errorClass":"UnsupportedOperationException","httpStatus":null,"severity":"error","filePath":"flink-datastream/src/main/java/org/apache/flink/datastream/impl/stream/AbstractDataStream.java","lineNumber":74,"sourceCode":"    }\n\n    public TypeInformation<T> getType() {\n        return transformation.getOutputType();\n    }\n\n    /** This is only used for internal implementation. It must not leak to user face api. */\n    public Transformation<T> getTransformation() {\n        return transformation;\n    }\n\n    public ExecutionEnvironmentImpl getEnvironment() {\n        return environment;\n    }\n\n    public <X> Transformation<X> getSideOutputTransform(OutputTag<X> outputTag) {\n        TypeInformation<?> type = requestedSideOutputs.get(outputTag);\n        if (type != null && !type.equals(outputTag.getTypeInfo())) {\n            throw new UnsupportedOperationException(\n                    \"A side output with a matching id was \"\n                            + \"already requested with a different type. This is not allowed, side output \"\n                            + \"ids need to be unique.\");\n        }\n        requestedSideOutputs.put(outputTag, outputTag.getTypeInfo());\n\n        return new SideOutputTransformation<>(getTransformation(), outputTag);\n    }\n}\n","sourceCodeStart":56,"sourceCodeEnd":84,"githubUrl":"https://github.com/apache/flink/blob/2f3c205e9266cb30240eb7f4fdab15cad629a70f/flink-datastream/src/main/java/org/apache/flink/datastream/impl/stream/AbstractDataStream.java#L56-L84","documentation":"Error \"A side output with a matching id was already requested with a different type. This is not allowed, side output ids need to be unique.\" thrown in apache/flink.","triggerScenarios":"Triggered at runtime when the operation fails because: A side output with a matching id was already requested with a different type. This is not allowed, side output ids need to be unique.","commonSituations":"Commonly caused by misconfiguration, missing dependencies or files, unsupported types or operations, or invalid user input leading to: A side output with a matching id was already requested with a different type. This is not allowed, side output ids need to be unique.","solutions":["Address the cause reported by the error message: A side output with a matching id was already requested with a different type. This is not allowed, side output ids need to be unique.","Verify the inputs, configuration values, and classpath/dependency setup related to this operation, then retry."],"exampleFix":"Correct the condition described (\"A side output with a matching id was already requested with a different type. This is not allowed, side output ids need to be unique.\") 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"}