[GitHub] [arrow-rs] alamb commented on a diff in pull request #1677: Fix generate_unions_case for Rust case

[GitBox <gi...@apache.org>]

alamb commented on code in PR #1677:
URL: https://github.com/apache/arrow-rs/pull/1677#discussion_r869664364


##########
arrow/src/datatypes/datatype.rs:
##########
@@ -499,6 +499,52 @@ impl DataType {
                         ))
                     }
                 }
+                Some(s) if s == "union" => {
+                    if let Some(Value::String(mode)) = map.get("mode") {
+                        let union_mode = if mode == "SPARSE" {
+                            UnionMode::Sparse
+                        } else if mode == "DENSE" {
+                            UnionMode::Dense
+                        } else {
+                            return Err(ArrowError::ParseError(format!(
+                                "Unknown union mode {:?} for union",
+                                mode
+                            )));
+                        };
+                        if let Some(type_ids) = map.get("typeIds") {
+                            let type_ids = type_ids
+                                .as_array()
+                                .unwrap()
+                                .iter()
+                                .map(|t| t.as_i64().unwrap())
+                                .collect::<Vec<_>>();
+
+                            let default_fields = type_ids
+                                .iter()
+                                .map(|t| {
+                                    Field::new("", DataType::Boolean, true).with_metadata(

Review Comment:
   is it cool to have a field without a name 🤔 



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