milesgranger commented on code in PR #14106:
URL: https://github.com/apache/arrow/pull/14106#discussion_r972937826
##########
cpp/src/arrow/compute/kernels/scalar_cast_numeric.cc:
##########
@@ -769,6 +770,36 @@ std::vector<std::shared_ptr<CastFunction>>
GetNumericCasts() {
return functions;
}
+
+Status CastToExtension(KernelContext* ctx, const ExecSpan& batch, ExecResult*
out) {
+ const CastOptions& options = checked_cast<const
CastState*>(ctx->state())->options;
+ DCHECK(batch[0].is_array());
+ std::shared_ptr<Array> array = batch[0].array.ToArray();
+ std::shared_ptr<Array> result;
+
+ auto out_ty = GetExtensionType("arrow.py_integer_type")->storage_type();
+ RETURN_NOT_OK(Cast(*array, out_ty, options,
+ ctx->exec_context())
+ .Value(&result));
+
+ ExtensionArray extension(options.to_type.GetSharedPtr(), result);
+ out->value = std::move(extension.data());
+ return Status::OK();
+}
Review Comment:
I can make it work by templating `GetCastToExtension` and `CastToExtension`
then adding the kernel as such:
```cpp
template <typename StorageType>
std::shared_ptr<CastFunction> GetCastToExtension(std::string name) {
auto func = std::make_shared<CastFunction>(std::move(name),
Type::EXTENSION);
DCHECK_OK(func->AddKernel(Type::INT64, {InputType(Type::INT64)},
kOutputTargetType, CastToExtension<StorageType>));
return func;
}
std::vector<std::shared_ptr<CastFunction>> GetExtensionCasts() {
auto func = GetCastToExtension<Int64Type>("cast_extension");
return {func};
}
```
Where the templated type is the possible storage types of the extension
type. Maybe there is a more slick way to accomplish it, especially since the
extension name is in the registry, as demonstrated by the hard-coded impl; but
will continue with this for now. :)
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