tustvold opened a new issue #1217:
URL: https://github.com/apache/arrow-rs/issues/1217


   **Is your feature request related to a problem or challenge? Please describe 
what you are trying to do.**
   
   A schema Field currently has a `dict_is_ordered` field. Much like `dict_id` 
this is non-trivial to use in practice (#1206), as it is part of the schema 
which may need to remain constant across multiple RecordBatch, that would wish 
to use different dictionaries. It is also not visible to compute kernels.
   
   There doesn't appear to be a notion of if a dictionary contains unique 
values.
   
   **Describe the solution you'd like**
   
   We would ideally like to associated dictionary properties with the 
dictionary arrays themselves. This would allow compute kernels to exploit their 
properties, in addition to avoiding schema incompatibility issues.
   
   There is an assumption in many places that the arrays themselves are sugar 
on top of `ArrayData`, with it possible to construct a DictionaryArray from a 
`ArrayData`. As such I would like to propose:
   
   * Remove dict_is_ordered from Field
   * Add dict_is_ordered bool to ArrayData (default false)
   * Add dict_is_unique bool to ArrayData (default false)
   
   The various compute kernels can then progressively be updated to exploit 
these properties.


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