[I] Dictionary "ordered" flag is not preserved when importing an FFI (C Data Interface) schema [arrow-rs]

["borchero (via GitHub)" <gi...@apache.org>]

borchero opened a new issue, #10513:
URL: https://github.com/apache/arrow-rs/issues/10513

   ### Describe the bug
   
   When converting an `FFI_ArrowSchema` (C Data Interface) into a Rust Field, the dictionary ordered flag is silently dropped. The C Data Interface encodes this via the `ARROW_FLAG_DICTIONARY_ORDERED` bit (`0b1`) in `ArrowSchema.flags`, and `FFI_ArrowSchema::dictionary_ordered()` reads it correctly — but `impl TryFrom<&FFI_ArrowSchema>` for `Field` never applies it to the resulting `Field`. As a result, a dictionary field that is exported with `dict_is_ordered = true` always comes back as `dict_is_ordered = false` after a round trip through the FFI schema.
   
   ### To Reproduce
   
   ```rust
   use arrow_schema::{DataType, Field};
   use arrow_schema::ffi::FFI_ArrowSchema;
   
   let field = Field::new(
       "dict",
       DataType::Dictionary(Box::new(DataType::Int32), Box::new(DataType::Utf8)),
       false,
   )
   .with_dict_is_ordered(true);
   
   // Export to the C Data Interface and import back.
   let ffi = FFI_ArrowSchema::try_from(&field).unwrap();
   assert!(ffi.dictionary_ordered()); // OK — flag is set on the FFI schema
   
   let roundtripped = Field::try_from(&ffi).unwrap();
   assert_eq!(roundtripped.dict_is_ordered(), Some(true)); // FAILS: returns Some(false)
   ```
   
   
   ### Expected behavior
   
   Importing an `FFI_ArrowSchema` whose `DICTIONARY_ORDERED` flag is set should produce a `Field` with `dict_is_ordered() == Some(true)`, so that exporting and re-importing a dictionary field is a lossless round trip.
   
   ### Additional context
   
   _No response_


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Re: [I] Dictionary "ordered" flag is not preserved when importing an FFI (C Data Interface) schema [arrow-rs]

["Jefffrey (via GitHub)" <gi...@apache.org>]

Jefffrey closed issue #10513: Dictionary "ordered" flag is not preserved when importing an FFI (C Data Interface) schema
URL: https://github.com/apache/arrow-rs/issues/10513


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