{"record":{"id":"c7b9bb10b85b50d6","repo":"pathwaycom/pathway","slug":"incompatible-types-for-function-name-operation","errorCode":null,"errorMessage":"Incompatible types for {function_name} operation.\\nThe types are: {dtypes}. {Affected column: '{key}'. }You might try casting the id type to pw.Pointer to circumvent this, but this is most probably an error.","messagePattern":"Incompatible types for (.+?) operation\\.\\\\nThe types are: (.+?)\\. (.+?)'\\. \\}You might try casting the id type to pw\\.Pointer to circumvent this, but this is most probably an error\\.","errorType":"exception","errorClass":"TypeError","httpStatus":null,"severity":"error","filePath":"python/pathway/internals/table.py","lineNumber":3264,"sourceCode":"            raising=True,\n        )\n    except TypeError:\n        msg = (\n            f\"Incompatible types for {function_name} operation.\\n\"\n            + f\"The types are: {dtypes}. \"\n            + (f\"Affected column: '{key}'. \" if key is not None else \"\")\n        )\n        if pointers:\n            msg += (\n                \"You might try casting the id type to pw.Pointer to circumvent this, \"\n                + \"but this is most probably an error.\"\n            )\n        else:\n            msg += (\n                \"You might try casting the expressions to Any type to circumvent this, \"\n                + \"but this is most probably an error.\"\n            )\n        raise TypeError(msg)\n","sourceCodeStart":3246,"sourceCodeEnd":3265,"githubUrl":"https://github.com/pathwaycom/pathway/blob/fa2f74a4649b7c5908690cf60137263d8d80de5f/python/pathway/internals/table.py#L3246-L3265","documentation":"Raised by Pathway's binary-operation type checking (e.g. arithmetic/comparison between columns, joins on keys) when operand dtypes are incompatible — no common supertype exists. The message lists the types, the affected column, and suggests (for pointers) casting the id type to pw.Pointer or (otherwise) casting expressions to Any as an explicit, likely-wrong workaround.","triggerScenarios":"t1.join(t2, t1.id == t2.id) where id dtypes are different Pointer subtypes; pw.this.a + pw.this.b with int and str columns; comparing columns whose dtypes have no common supertype.","commonSituations":"Joining tables from different connectors with differently typed key columns; performing arithmetic on mixed-type columns after schema changes; ids built from different value types across pipelines.","solutions":["Cast one side so dtypes match: t1.join(t2, t1.key.cast(str) == t2.key) or use cast_to_types before the operation","For id/pointer mismatches, unify id types: t1.update_id_type(pw.Pointer()) or rebuild ids from the same value type","As a last resort for genuinely heterogeneous data, cast both to Any as the message suggests — but treat it as a smell","Inspect dtypes first: t.eval_type(pw.this.col) on each operand to see the exact mismatch"],"exampleFix":"# before\nt3 = t1.join(t2, t1.key == t2.key)  # Pointer[int] vs Pointer[str] -> TypeError\n\n# after\nt3 = t1.join(t2, t1.key.cast(str).is_in(t2.key))\n# or unify id types\nt3 = t1.update_id_type(pw.Pointer()).join(t2, pw.left.id == pw.right.id)","handlingStrategy":"type-guard","validationCode":"from pathway.internals import dtype as dt\n\ndef operands_compatible(a, b) -> bool:\n    try:\n        dt.types_lattice_common_type_binary(a, b)\n        return True\n    except TypeError:\n        return False","typeGuard":"def common_type_exists(dtype_getter, *exprs):\n    from pathway.internals import dtype as dt\n    ds = [dtype_getter(e) for e in exprs]\n    try:\n        dt.types_lattice_common_type_many(ds)\n        return True\n    except TypeError:\n        return False","tryCatchPattern":"try:\n    t3 = t1.join(t2, t1.k == t2.k)\nexcept TypeError as e:\n    if 'Incompatible types' in str(e):\n        t3 = t1.join(t2, t1.k.cast(str) == t2.k.cast(str))","preventionTips":["Cast join keys to one type explicitly","Standardize id types across connectors at ingestion","Treat the pw.Pointer/Any cast workaround as a red flag, not a fix"],"tags":["pathway","typing","binary-op","join"],"backgroundTag":null,"analyzedSha":"fa2f74a4649b7c5908690cf60137263d8d80de5f","analyzedAt":"2026-08-15T01:48:17.006Z","schemaVersion":2},"datasetVersion":"2026-08-15T17:31:12.345Z"}