Hi Micah,

Oh! I missed the part... I only read
https://arrow.apache.org/docs/format/Columnar.html . Sorry.

Thanks,
-- 
kou

In <cak7z5t-wm1r92hgnetq88fncrlruiijdxg07aohzvry1qzk...@mail.gmail.com>
  "Re: Map type's key/item/value field names" on Tue, 3 Mar 2026 22:36:36 -0800,
  Micah Kornfield <[email protected]> wrote:

> Hi Kou,
> I think this might be based on the spec [1]:
> 
> "The names of the child fields may be respectively "entries", "key", and
> "value", but this is not enforced."
> 
> Cheers,
> Micah
> 
> 
> [1] https://github.com/apache/arrow/blob/main/format/Schema.fbs#L128
> 
> On Tue, Mar 3, 2026 at 9:14 PM Sutou Kouhei <[email protected]> wrote:
> 
>> Hi,
>>
>> Recently, I'm implementing pure Ruby Apache Arrow reader and
>> writer. Currently, I've added the pure Ruby implementation
>> to our integration test:
>> https://github.com/apache/arrow/pull/49423
>>
>> I noticed that the C++ implementation ignores key/item/value
>> field names of map type ("key"/"value"/"entries" are always
>> used) in the work:
>> https://github.com/apache/arrow/issues/49415
>>
>> I've fixed it: https://github.com/apache/arrow/pull/49416
>>
>> But I also noticed that the .NET/Go/JS implementations also
>> ignores key/item/value field names of map type
>> ("key"/"value"/"entries" are always used). The Rust
>> implementation and nanoarrow use field names in Apache Arrow
>> data.
>>
>> I think that key/item/value field names of map type in
>> Apache Arrow data should not be ignored. Is it correct?
>>
>> If it's correct, should we validate the behavior in our
>> integration test?
>>
>> I've added "no_map_field_names_validate" quirk in
>> https://github.com/apache/arrow/pull/49423 to control
>> whether we should validate map field names or not.
>>
>>
>> Thanks,
>> --
>> kou
>>

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