Hi folks,
arrow::MakeBuilder function with a dictionary type creates a
dictionary builder with AdaptiveIntBuilder by ignoring the bit-width
of DictionaryType's index type.
I want to know whether this behavior is intentional or not.
I think this feature is useful when I want to use a dictionary builder
with AdaptiveIntBuilder.
But the result by following code is a little bit surprising.
```cpp
#include <arrow/api.h>
#include <arrow/util/logging.h>
#include <iostream>
int
main(int argc, char **argv)
{
auto dict_type = arrow::dictionary(arrow::int32(), arrow::utf8());
std::unique_ptr<arrow::ArrayBuilder> out;
ARROW_CHECK_OK(arrow::MakeBuilder(arrow::default_memory_pool(),
dict_type, &out));
std::cout << "type: " << out->type()->ToString() << std::endl;
return 0;
}
```
You can see the message below when executing this code.
type: dictionary<values=string, indices=int8, ordered=0>
I got `indices=int8` from a dictionary type with int32 index type.
I guess most people expect they get `indices=int32` here.
--
Kenta Murata
