{"record":{"id":"746102c6dfe6c6ae","repo":"pathwaycom/pathway","slug":"failed-to-parse-dtype-from-dict-data","errorCode":null,"errorMessage":"Failed to parse DType from dict: {data}","messagePattern":"Failed to parse DType from dict: (.+?)","errorType":"exception","errorClass":"ValueError","httpStatus":null,"severity":"error","filePath":"python/pathway/internals/dtype.py","lineNumber":1101,"sourceCode":"    \"BYTES\": BYTES,\n    \"DATE_TIME_NAIVE\": DATE_TIME_NAIVE,\n    \"DATE_TIME_UTC\": DATE_TIME_UTC,\n    \"DURATION\": DURATION,\n    \"Json\": JSON,\n    \"NONE\": NONE,\n    \"ANY\": ANY,\n    \"PY_OBJECT_WRAPPER\": ANY_PY_OBJECT_WRAPPER,\n    \"POINTER\": ANY_POINTER,\n}\n\n\ndef parse_dtype_from_dict(data: dict) -> DType:\n    type_name = data[\"type\"]\n    if type_name in NON_COMPOSITE_DTYPES:\n        return NON_COMPOSITE_DTYPES[type_name]\n    if type_name in COMPOSITE_DTYPES:\n        return COMPOSITE_DTYPES[type_name](data)\n    raise ValueError(f\"Failed to parse DType from dict: {data}\")\n","sourceCodeStart":1083,"sourceCodeEnd":1102,"githubUrl":"https://github.com/pathwaycom/pathway/blob/fa2f74a4649b7c5908690cf60137263d8d80de5f/python/pathway/internals/dtype.py#L1083-L1102","documentation":"parse_dtype_from_dict reconstructs a DType from its serialized dictionary form (a {'type': <NAME>} payload used when persisting/communicating schemas). It only knows the fixed sets NON_COMPOSITE_DTYPES and COMPOSITE_DTYPES; an unknown 'type' name means the payload was produced by a different (usually newer or older) Pathway version or was hand-crafted/edited.","triggerScenarios":"Restoring a persisted state or replaying a schema dump created by a different Pathway version that introduced a dtype name this build's dicts don't contain; manually constructing or mutating the serialized dtype dict; corrupted IPC/serialization payloads crossing version boundaries.","commonSituations":"Upgrading/downgrading Pathway while keeping persistent storage; running mixed-version clusters or worker containers; editing serialized pipeline definitions by hand.","solutions":["Pin all processes that read/write the serialized dtypes to the same Pathway version (check pip show pathway everywhere)","Regenerate the serialized schema/dict from scratch in the current version instead of reusing old files","If the payload must be read, pre-validate data['type'] against the keys in pathway.internals.dtype.NON_COMPOSITE_DTYPES / COMPOSITE_DTYPES and migrate unknown names explicitly"],"exampleFix":"// before\ndtype = parse_dtype_from_dict(loaded_payload)\n// after\nfrom pathway.internals.dtype import NON_COMPOSITE_DTYPES, COMPOSITE_DTYPES, parse_dtype_from_dict\nassert loaded_payload[\"type\"] in {**NON_COMPOSITE_DTYPES, **COMPOSITE_DTYPES}, f\"dtype from another version: {loaded_payload['type']}\"\ndtype = parse_dtype_from_dict(loaded_payload)","handlingStrategy":"validation","validationCode":"from pathway.internals.dtype import NON_COMPOSITE_DTYPES, COMPOSITE_DTYPES\n\ndef can_parse_dtype(data: dict) -> bool:\n    return isinstance(data, dict) and data.get(\"type\") in {**NON_COMPOSITE_DTYPES, **COMPOSITE_DTYPES}","typeGuard":null,"tryCatchPattern":"try:\n    parse_dtype_from_dict(data)\nexcept ValueError as e:\n    if \"Failed to parse DType\" in str(e):\n        log.error(\"serialized dtype from a different pathway version\", payload=data)","preventionTips":["Pin one pathway version across all processes that share persisted state","Regenerate serialized schemas after upgrading instead of reusing old payloads","Validate the 'type' key against the known dtype name sets before parsing"],"tags":["pathway","dtype","serialization","version-mismatch","persistence"],"backgroundTag":null,"analyzedSha":"fa2f74a4649b7c5908690cf60137263d8d80de5f","analyzedAt":"2026-08-15T01:48:17.006Z","schemaVersion":2},"datasetVersion":"2026-08-15T22:17:37.221Z"}