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The following commit(s) were added to refs/heads/main by this push:
new 800425cee0 refactor: improve display formatting for Union (#8529)
800425cee0 is described below
commit 800425cee0cfed63b581c5bb216e8bc65fdcb956
Author: Alex Huang <[email protected]>
AuthorDate: Sat Oct 4 13:32:47 2025 +0300
refactor: improve display formatting for Union (#8529)
# Which issue does this PR close?
- Parts of #8351
# Rationale for this change
Support more human readable display in `Union`
# What changes are included in this PR?
# Are these changes tested?
Yes
# Are there any user-facing changes?
No
---------
Co-authored-by: Andrew Lamb <[email protected]>
---
arrow-schema/src/datatype_display.rs | 84 +++++++++++++++++++++++++++++++++++-
1 file changed, 83 insertions(+), 1 deletion(-)
diff --git a/arrow-schema/src/datatype_display.rs
b/arrow-schema/src/datatype_display.rs
index 73ceb3f680..6e9501777a 100644
--- a/arrow-schema/src/datatype_display.rs
+++ b/arrow-schema/src/datatype_display.rs
@@ -132,7 +132,24 @@ impl fmt::Display for DataType {
Ok(())
}
Self::Union(union_fields, union_mode) => {
- write!(f, "Union({union_fields:?}, {union_mode:?})")
+ write!(f, "Union({union_mode:?}, ")?;
+ if !union_fields.is_empty() {
+ let fields_str = union_fields
+ .iter()
+ .map(|v| {
+ let type_id = v.0;
+ let field = v.1;
+ let maybe_nullable = if field.is_nullable() {
"nullable " } else { "" };
+ let data_type = field.data_type();
+ let metadata_str =
format_metadata(field.metadata());
+ format!("{type_id:?}:
{maybe_nullable}{data_type}{metadata_str}")
+ })
+ .collect::<Vec<_>>()
+ .join(", ");
+ write!(f, "{fields_str}")?;
+ }
+ write!(f, ")")?;
+ Ok(())
}
Self::Dictionary(data_type, data_type1) => {
write!(f, "Dictionary({data_type}, {data_type1})")
@@ -248,4 +265,69 @@ mod tests {
"FixedSizeList(4 x nullable Int32, metadata: {\"key2\":
\"value2\"})";
assert_eq!(fixed_size_metadata_string, expected_metadata_string);
}
+
+ #[test]
+ fn test_display_struct() {
+ let fields = vec![
+ Field::new("a", DataType::Int32, false),
+ Field::new("b", DataType::Utf8, true),
+ ];
+ let struct_data_type = DataType::Struct(fields.into());
+ let struct_data_type_string = struct_data_type.to_string();
+ let expected_string = "Struct(\"a\": Int32, \"b\": nullable Utf8)";
+ assert_eq!(struct_data_type_string, expected_string);
+
+ // Test with metadata
+ let mut field_with_metadata = Field::new("b", DataType::Utf8, true);
+ let metadata = HashMap::from([("key".to_string(),
"value".to_string())]);
+ field_with_metadata.set_metadata(metadata);
+ let struct_fields_with_metadata =
+ vec![Field::new("a", DataType::Int32, false), field_with_metadata];
+ let struct_data_type_with_metadata =
DataType::Struct(struct_fields_with_metadata.into());
+ let struct_data_type_with_metadata_string =
struct_data_type_with_metadata.to_string();
+ let expected_string_with_metadata =
+ "Struct(\"a\": Int32, \"b\": nullable Utf8, metadata: {\"key\":
\"value\"})";
+ assert_eq!(
+ struct_data_type_with_metadata_string,
+ expected_string_with_metadata
+ );
+ }
+
+ #[test]
+ fn test_display_union() {
+ let fields = vec![
+ Field::new("a", DataType::Int32, false),
+ Field::new("b", DataType::Utf8, true),
+ ];
+ let type_ids = vec![0, 1];
+ let union_fields = type_ids
+ .into_iter()
+ .zip(fields.into_iter().map(Arc::new))
+ .collect();
+
+ let union_data_type = DataType::Union(union_fields,
crate::UnionMode::Sparse);
+ let union_data_type_string = union_data_type.to_string();
+ let expected_string = "Union(Sparse, 0: Int32, 1: nullable Utf8)";
+ assert_eq!(union_data_type_string, expected_string);
+
+ // Test with metadata
+ let mut field_with_metadata = Field::new("b", DataType::Utf8, true);
+ let metadata = HashMap::from([("key".to_string(),
"value".to_string())]);
+ field_with_metadata.set_metadata(metadata);
+ let union_fields_with_metadata = vec![
+ (0, Arc::new(Field::new("a", DataType::Int32, false))),
+ (1, Arc::new(field_with_metadata)),
+ ]
+ .into_iter()
+ .collect();
+ let union_data_type_with_metadata =
+ DataType::Union(union_fields_with_metadata,
crate::UnionMode::Sparse);
+ let union_data_type_with_metadata_string =
union_data_type_with_metadata.to_string();
+ let expected_string_with_metadata =
+ "Union(Sparse, 0: Int32, 1: nullable Utf8, metadata: {\"key\":
\"value\"})";
+ assert_eq!(
+ union_data_type_with_metadata_string,
+ expected_string_with_metadata
+ );
+ }
}
