{"record":{"id":"d06ffa22bb8a2b84","repo":"pola-rs/polars","slug":"iceberg-unknown-value-for-reader-override-read","errorCode":null,"errorMessage":"iceberg: unknown value for reader_override: '{reader_override}', expected one of ('native', 'pyiceberg')","messagePattern":"iceberg: unknown value for reader_override: '(.+?)', expected one of \\('native', 'pyiceberg'\\)","errorType":"exception","errorClass":"ValueError","httpStatus":null,"severity":"error","filePath":"py-polars/src/polars/io/iceberg/_dataset.py","lineNumber":356,"sourceCode":"            if verbose:\n                eprint(\n                    \"IcebergScanResolver: to_dataset_scan(): early return \"\n                    f\"({snapshot_id_key = })\"\n                )\n\n            return None\n\n        # Take from parameter first then envvar\n        reader_override = self.reader_override or os.getenv(\n            \"POLARS_ICEBERG_READER_OVERRIDE\"\n        )\n\n        if reader_override and reader_override not in [\"native\", \"pyiceberg\"]:\n            msg = (\n                \"iceberg: unknown value for reader_override: \"\n                f\"'{reader_override}', expected one of ('native', 'pyiceberg')\"\n            )\n            raise ValueError(msg)\n\n        fallback_reason = (\n            \"forced reader_override='pyiceberg'\"\n            if reader_override == \"pyiceberg\"\n            else None\n        )\n\n        selected_fields = (\"*\",) if projection is None else tuple(projection)\n\n        projected_iceberg_schema = (\n            iceberg_schema\n            if selected_fields == (\"*\",)\n            else iceberg_schema.select(*selected_fields)\n        )\n\n        initial_defaults = {\n            x: value\n            for x in projected_iceberg_schema.field_ids","sourceCodeStart":338,"sourceCodeEnd":374,"githubUrl":"https://github.com/pola-rs/polars/blob/df599052daf96e7a9cc30a3b0c6bd25d6947e3c0/py-polars/src/polars/io/iceberg/_dataset.py#L338-L374","documentation":"Error \"iceberg: unknown value for reader_override: '{reader_override}', expected one of ('native', 'pyiceberg')\" thrown in pola-rs/polars.","triggerScenarios":"Thrown at py-polars/src/polars/io/iceberg/_dataset.py:356 when the library encounters an invalid state.","commonSituations":"See trigger scenarios.","solutions":[],"exampleFix":null,"handlingStrategy":null,"validationCode":null,"typeGuard":null,"tryCatchPattern":null,"preventionTips":[],"tags":[],"backgroundTag":null,"analyzedSha":"df599052daf96e7a9cc30a3b0c6bd25d6947e3c0","analyzedAt":"2026-08-16T12:10:03.978Z","schemaVersion":2},"datasetVersion":"2026-08-16T13:17:31.715Z"}