WillAyd commented on a change in pull request #12248:
URL: https://github.com/apache/arrow/pull/12248#discussion_r802208121
##########
File path: cpp/src/arrow/compute/kernels/scalar_cast_nested.cc
##########
@@ -150,6 +150,80 @@ void AddListCast(CastFunction* func) {
DCHECK_OK(func->AddKernel(SrcType::type_id, std::move(kernel)));
}
+struct CastStruct {
+ static Status Exec(KernelContext* ctx, const ExecBatch& batch, Datum* out) {
+ const CastOptions& options = CastState::Get(ctx);
+ const auto in_field_count =
+ checked_cast<const StructType&>(*batch[0].type()).num_fields();
+ const auto out_field_count =
+ checked_cast<const StructType&>(*out->type()).num_fields();
+
+ if (in_field_count != out_field_count) {
+ return Status::TypeError("struct field sizes do not match: ",
+ batch[0].type()->ToString(), " ",
out->type()->ToString());
+ }
+
+ for (int64_t i = 0; i < in_field_count; ++i) {
+ const auto in_field_name =
+ checked_cast<const StructType&>(*batch[0].type()).field(i)->name();
+ const auto out_field_name =
+ checked_cast<const StructType&>(*out->type()).field(i)->name();
Review comment:
Actually had this backwards before, but the current implementation is
doing what you are describing. I think CheckCast has the wrong expectation
given the below output:
```
Expected:
-- is_valid: all not null
-- child 0 type: int8
[
1,
null
]
-- child 1 type: int8
[
3,
4
]
Actual:
-- is_valid: all not null
-- child 0 type: int8
[
1,
2
]
-- child 1 type: int8
[
3,
4
]
```
Do I have that right? If so would you suggest trying to change CheckCast or
would it be better to not use that function?
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