nevi-me commented on a change in pull request #8291:
URL: https://github.com/apache/arrow/pull/8291#discussion_r497137450
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File path: rust/arrow/src/ipc/convert.rs
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@@ -609,10 +621,45 @@ pub(crate) fn get_fb_field_type<'a: 'b, 'b>(
children: Some(fbb.create_vector(&children[..])),
}
}
+ Dictionary(_, value_type) => {
+ // In this library, the dictionary "type" is a logical construct.
Here we
+ // pass through to the value type, as we've already captured the
index
+ // type in the DictionaryEncoding metadata in the parent field
+ get_fb_field_type(value_type, fbb)
+ }
t => unimplemented!("Type {:?} not supported", t),
}
}
+/// Create an IPC dictionary encoding
+pub(crate) fn get_fb_dictionary<'a: 'b, 'b>(
+ index_type: &DataType,
+ dict_id: i64,
+ dict_is_ordered: bool,
+ fbb: &mut FlatBufferBuilder<'a>,
+) -> WIPOffset<ipc::DictionaryEncoding<'b>> {
+ // We assume that the dictionary index type (as an integer) has already
been
+ // validated elsewhere, and can safely assume we are dealing with signed
+ // integers
+ let mut index_builder = ipc::IntBuilder::new(fbb);
+ index_builder.add_is_signed(true);
Review comment:
Although signed indices are preferred, we do support unsigned dictionary
indices in the data types, so we might need to populate this based on the
`index_type`
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