Agreed.
I made ARROW-9642 and its pull-request.
https://github.com/apache/arrow/pull/7898
2020年8月4日(火) 6:32 Wes McKinney <wesmck...@gmail.com>:
>
> It seems useful to use the index type to set the starting bit width of
> the builder. I guess we can preserve the behavior of expanding to the
> next bit width when overflowing the smaller integer types.
>
> On Sun, Aug 2, 2020 at 9:32 PM Kenta Murata <mura...@gmail.com> wrote:
> >
> > 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
--
Regards,
Kenta Murata
