paleolimbot commented on code in PR #13397:
URL: https://github.com/apache/arrow/pull/13397#discussion_r918308915
##########
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");
Review Comment:
I updated this - a user might get this error if the scalar function author
provided an R function as a type resolver and it didn't return the right thing
(more likely a scalar function author would get the error when writing tests
which hopefully they do if they're using that feature).
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