rtpsw commented on code in PR #14682: URL: https://github.com/apache/arrow/pull/14682#discussion_r1049561525
########## python/pyarrow/src/arrow/python/udf.cc: ########## @@ -105,21 +158,117 @@ Status RegisterScalarFunction(PyObject* user_function, ScalarUdfWrapperCallback } compute::OutputType output_type(options.output_type); auto udf_data = std::make_shared<PythonUdf>( - wrapper, std::make_shared<OwnedRefNoGIL>(user_function), options.output_type); + std::make_shared<OwnedRefNoGIL>(user_function), wrapper, options.output_type); compute::ScalarKernel kernel( compute::KernelSignature::Make(std::move(input_types), std::move(output_type), options.arity.is_varargs), - PythonUdfExec); + PythonUdfExec, kernel_init); kernel.data = std::move(udf_data); kernel.mem_allocation = compute::MemAllocation::NO_PREALLOCATE; kernel.null_handling = compute::NullHandling::COMPUTED_NO_PREALLOCATE; RETURN_NOT_OK(scalar_func->AddKernel(std::move(kernel))); - auto registry = compute::GetFunctionRegistry(); + if (registry == NULLPTR) { + registry = compute::GetFunctionRegistry(); + } RETURN_NOT_OK(registry->AddFunction(std::move(scalar_func))); return Status::OK(); } -} // namespace py +} // namespace + +Status RegisterScalarFunction(PyObject* user_function, ScalarUdfWrapperCallback wrapper, + const ScalarUdfOptions& options, + compute::FunctionRegistry* registry) { + return RegisterScalarLikeFunction( + user_function, + PythonScalarUdfKernelInit{std::make_shared<OwnedRefNoGIL>(user_function)}, wrapper, + options, registry); +} + +Status RegisterTabularFunction(PyObject* user_function, ScalarUdfWrapperCallback wrapper, + const ScalarUdfOptions& options, + compute::FunctionRegistry* registry) { + if (options.arity.num_args != 0 || options.arity.is_varargs) { + return Status::NotImplemented("tabular function of non-null arity"); + } + if (options.output_type->id() != Type::type::STRUCT) { + return Status::Invalid("tabular function with non-struct output"); + } + return RegisterScalarLikeFunction( + user_function, + PythonTableUdfKernelInit{std::make_shared<OwnedRefNoGIL>(user_function), wrapper}, + wrapper, options, registry); +} +namespace { + +Result<std::shared_ptr<RecordBatch>> RecordBatchFromArray( + std::shared_ptr<Schema> schema, std::shared_ptr<Array> array) { + auto& data = const_cast<std::shared_ptr<ArrayData>&>(array->data()); + if (data->child_data.size() != static_cast<size_t>(schema->num_fields())) { + return Status::Invalid("UDF result with shape not conforming to schema"); + } + return RecordBatch::Make(std::move(schema), data->length, std::move(data->child_data)); +} + +} // namespace + +Result<std::shared_ptr<RecordBatchReader>> CallTabularFunction( + const std::string& func_name, const std::vector<Datum>& args, + compute::FunctionRegistry* registry) { + if (args.size() != 0) { + return Status::NotImplemented("non-empty arguments to tabular function"); + } + if (registry == NULLPTR) { + registry = compute::GetFunctionRegistry(); + } + ARROW_ASSIGN_OR_RAISE(auto func, registry->GetFunction(func_name)); + if (func->kind() != compute::Function::SCALAR) { + return Status::Invalid("tabular function of non-scalar kind"); + } + auto arity = func->arity(); + if (arity.num_args != 0 || arity.is_varargs) { + return Status::NotImplemented("tabular function of non-null arity"); + } + auto kernels = + arrow::internal::checked_pointer_cast<compute::ScalarFunction>(func)->kernels(); + if (kernels.size() != 1) { + return Status::NotImplemented("tabular function with non-single kernel"); + } + const compute::ScalarKernel* kernel = kernels[0]; + auto out_type = kernel->signature->out_type(); + if (out_type.kind() != compute::OutputType::FIXED) { + return Status::Invalid("tabular kernel of non-fixed kind"); + } + auto datatype = out_type.type(); + if (datatype->id() != Type::type::STRUCT) { + return Status::Invalid("tabular kernel with non-struct output"); + } + auto struct_type = arrow::internal::checked_cast<StructType*>(datatype.get()); + auto schema = ::arrow::schema(struct_type->fields()); + std::vector<TypeHolder> in_types; + ARROW_ASSIGN_OR_RAISE(auto func_exec, + GetFunctionExecutor(func_name, in_types, NULLPTR, registry)); + auto next_func = + [schema, + func_exec = std::move(func_exec)]() -> Result<std::shared_ptr<RecordBatch>> { + std::vector<Datum> args; + // passed_length of -1 or 0 with args.size() of 0 leads to an empty ExecSpanIterator + // in exec.cc and to never invoking the source function, so 1 is passed instead + ARROW_ASSIGN_OR_RAISE(auto datum, func_exec->Execute(args, /*passed_length=*/1)); + if (!datum.is_array()) { + return Status::Invalid("UDF result of non-array kind"); + } + std::shared_ptr<Array> array = datum.make_array(); + if (array->length() == 0) { + return IterationTraits<std::shared_ptr<RecordBatch>>::End(); + } + return RecordBatchFromArray(std::move(schema), std::move(array)); Review Comment: Reviewing this, I believe I used `StructArray` because the [original result-handling code](https://github.com/apache/arrow/blob/5c1044fce55ed0e373a622cb8ee3b97a1a34799a/python/pyarrow/src/arrow/python/udf.cc#L68-L83) deals with arrays only, so introducing a new type of result should probably be done with care and consistency. 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