paleolimbot commented on code in PR #13397:
URL: https://github.com/apache/arrow/pull/13397#discussion_r918307791
##########
r/src/compute.cpp:
##########
@@ -574,3 +576,169 @@ SEXP compute__CallFunction(std::string func_name,
cpp11::list args, cpp11::list
std::vector<std::string> compute__GetFunctionNames() {
return arrow::compute::GetFunctionRegistry()->GetFunctionNames();
}
+
+class RScalarUDFKernelState : public arrow::compute::KernelState {
+ public:
+ RScalarUDFKernelState(cpp11::sexp exec_func, cpp11::sexp resolver)
+ : exec_func_(exec_func), resolver_(resolver) {}
+
+ cpp11::function exec_func_;
+ cpp11::function resolver_;
+};
+
+arrow::Result<arrow::TypeHolder> ResolveScalarUDFOutputType(
+ arrow::compute::KernelContext* context,
+ const std::vector<arrow::TypeHolder>& input_types) {
+ return SafeCallIntoR<arrow::TypeHolder>(
+ [&]() -> arrow::TypeHolder {
+ auto kernel =
+ reinterpret_cast<const
arrow::compute::ScalarKernel*>(context->kernel());
+ auto state =
std::dynamic_pointer_cast<RScalarUDFKernelState>(kernel->data);
+
+ cpp11::writable::list input_types_sexp(input_types.size());
+ for (size_t i = 0; i < input_types.size(); i++) {
+ input_types_sexp[i] =
+ cpp11::to_r6<arrow::DataType>(input_types[i].GetSharedPtr());
+ }
+
+ cpp11::sexp output_type_sexp = state->resolver_(input_types_sexp);
+ if (!Rf_inherits(output_type_sexp, "DataType")) {
+ cpp11::stop("arrow_scalar_function resolver must return a DataType");
+ }
+
+ return arrow::TypeHolder(
+ cpp11::as_cpp<std::shared_ptr<arrow::DataType>>(output_type_sexp));
+ },
+ "resolve scalar user-defined function output data type");
+}
+
+arrow::Status CallRScalarUDF(arrow::compute::KernelContext* context,
+ const arrow::compute::ExecSpan& span,
+ arrow::compute::ExecResult* result) {
+ if (result->is_array_span()) {
+ return arrow::Status::NotImplemented("ArraySpan result from R scalar UDF");
+ }
+
+ return SafeCallIntoRVoid(
+ [&]() {
+ auto kernel =
+ reinterpret_cast<const
arrow::compute::ScalarKernel*>(context->kernel());
+ auto state =
std::dynamic_pointer_cast<RScalarUDFKernelState>(kernel->data);
+
+ cpp11::writable::list args_sexp(span.num_values());
+
+ for (int i = 0; i < span.num_values(); i++) {
+ const arrow::compute::ExecValue& exec_val = span[i];
+ if (exec_val.is_array()) {
+ args_sexp[i] =
cpp11::to_r6<arrow::Array>(exec_val.array.ToArray());
+ } else if (exec_val.is_scalar()) {
+ args_sexp[i] =
cpp11::to_r6<arrow::Scalar>(exec_val.scalar->GetSharedPtr());
+ }
+ }
+
+ cpp11::sexp batch_length_sexp = cpp11::as_sexp(span.length);
+
+ std::shared_ptr<arrow::DataType> output_type =
result->type()->GetSharedPtr();
+ cpp11::sexp output_type_sexp =
cpp11::to_r6<arrow::DataType>(output_type);
+ cpp11::writable::list udf_context = {batch_length_sexp,
output_type_sexp};
+ udf_context.names() = {"batch_length", "output_type"};
+
+ cpp11::sexp func_result_sexp = state->exec_func_(udf_context,
args_sexp);
+
+ if (Rf_inherits(func_result_sexp, "Array")) {
+ auto array =
cpp11::as_cpp<std::shared_ptr<arrow::Array>>(func_result_sexp);
+
+ // handle an Array result of the wrong type
+ if (!result->type()->Equals(array->type())) {
+ arrow::Datum out = ValueOrStop(arrow::compute::Cast(array,
result->type()));
Review Comment:
I took this out - the "advanced" scalar function no longer casts the result
automatically (but the `arrow_scalar_function()` does, since if you do
something like `return(5)` in R you'll get a float64 Array. That auto-casting
there is handled in R (and there is skepticism at the advanced/non advanced
distinction and one of them might go away).
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