[Variant] Support shred_variant for Uuids (#8666)

# Which issue does this PR close?

- Closes #8665

# Rationale for this change
`shred_variant` currently panics when attempting to shred Variants
containing values of the FixedSizeBinary(16) data type

Author: friendlymatthew

parquet-variant-compute/src/shred_variant.rs

@@ -326,10 +326,11 @@ impl<'a> VariantToShreddedObjectVariantRowBuilder<'a> {
 mod tests {
     use super::*;
     use crate::VariantArrayBuilder;
-    use arrow::array::{Array, Float64Array, Int64Array};
+    use arrow::array::{Array, FixedSizeBinaryArray, Float64Array, Int64Array};
     use arrow::datatypes::{DataType, Field, Fields};
     use parquet_variant::{ObjectBuilder, ReadOnlyMetadataBuilder, Variant, VariantBuilder};
     use std::sync::Arc;
+    use uuid::Uuid;
 
     #[test]
     fn test_already_shredded_input_error() {
@@ -369,6 +370,73 @@ mod tests {
         shred_variant(&input, &list_schema).expect_err("unsupported");
     }
 
+    #[test]
+    fn test_invalid_fixed_size_binary_shredding() {
+        let mock_uuid_1 = Uuid::new_v4();
+
+        let input = VariantArray::from_iter([Some(Variant::from(mock_uuid_1)), None]);
+
+        // shred_variant only supports FixedSizeBinary(16). Any other length will err.
+        let err = shred_variant(&input, &DataType::FixedSizeBinary(17)).unwrap_err();
+
+        assert_eq!(
+            err.to_string(),
+            "Invalid argument error: FixedSizeBinary(17) is not a valid variant shredding type. Only FixedSizeBinary(16) for UUID is supported."
+        );
+    }
+
+    #[test]
+    fn test_uuid_shredding() {
+        let mock_uuid_1 = Uuid::new_v4();
+        let mock_uuid_2 = Uuid::new_v4();
+
+        let input = VariantArray::from_iter([
+            Some(Variant::from(mock_uuid_1)),
+            None,
+            Some(Variant::from(false)),
+            Some(Variant::from(mock_uuid_2)),
+        ]);
+
+        let variant_array = shred_variant(&input, &DataType::FixedSizeBinary(16)).unwrap();
+
+        // // inspect the typed_value Field and make sure it contains the canonical Uuid extension type
+        // let typed_value_field = variant_array
+        //     .inner()
+        //     .fields()
+        //     .into_iter()
+        //     .find(|f| f.name() == "typed_value")
+        //     .unwrap();
+
+        // assert!(
+        //     typed_value_field
+        //         .try_extension_type::<extension::Uuid>()
+        //         .is_ok()
+        // );
+
+        // probe the downcasted typed_value array to make sure uuids are shredded correctly
+        let uuids = variant_array
+            .typed_value_field()
+            .unwrap()
+            .as_any()
+            .downcast_ref::<FixedSizeBinaryArray>()
+            .unwrap();
+
+        assert_eq!(uuids.len(), 4);
+
+        assert!(!uuids.is_null(0));
+
+        let got_uuid_1: &[u8] = uuids.value(0);
+        assert_eq!(got_uuid_1, mock_uuid_1.as_bytes());
+
+        assert!(uuids.is_null(1));
+        assert!(uuids.is_null(2));
+
+        assert!(!uuids.is_null(3));
+
+        let got_uuid_2: &[u8] = uuids.value(3);
+        assert_eq!(got_uuid_2, mock_uuid_2.as_bytes());
+    }
+
     #[test]
     fn test_primitive_shredding_comprehensive() {
         // Test mixed scenarios in a single array
@@ -869,6 +937,187 @@ mod tests {
         assert!(value_field3.is_null(0)); // fully shredded, no remaining fields
     }
 
+    #[test]
+    fn test_uuid_shredding_in_objects() {
+        let mock_uuid_1 = Uuid::new_v4();
+        let mock_uuid_2 = Uuid::new_v4();
+        let mock_uuid_3 = Uuid::new_v4();
+
+        let mut builder = VariantArrayBuilder::new(6);
+
+        // Row 0: Fully shredded object with both UUID fields
+        builder
+            .new_object()
+            .with_field("id", mock_uuid_1)
+            .with_field("session_id", mock_uuid_2)
+            .finish();
+
+        // Row 1: Partially shredded object - UUID fields plus extra field
+        builder
+            .new_object()
+            .with_field("id", mock_uuid_2)
+            .with_field("session_id", mock_uuid_3)
+            .with_field("name", "test_user")
+            .finish();
+
+        // Row 2: Missing UUID field (no session_id)
+        builder.new_object().with_field("id", mock_uuid_1).finish();
+
+        // Row 3: Type mismatch - id is UUID but session_id is a string
+        builder
+            .new_object()
+            .with_field("id", mock_uuid_3)
+            .with_field("session_id", "not-a-uuid")
+            .finish();
+
+        // Row 4: Object with non-UUID value in id field
+        builder
+            .new_object()
+            .with_field("id", 12345i64)
+            .with_field("session_id", mock_uuid_1)
+            .finish();
+
+        // Row 5: Null
+        builder.append_null();
+
+        let input = builder.build();
+
+        let fields = Fields::from(vec![
+            Field::new("id", DataType::FixedSizeBinary(16), true),
+            Field::new("session_id", DataType::FixedSizeBinary(16), true),
+        ]);
+        let target_schema = DataType::Struct(fields);
+
+        let result = shred_variant(&input, &target_schema).unwrap();
+
+        assert!(result.value_field().is_some());
+        assert!(result.typed_value_field().is_some());
+        assert_eq!(result.len(), 6);
+
+        let metadata = result.metadata_field();
+        let value = result.value_field().unwrap();
+        let typed_value = result
+            .typed_value_field()
+            .unwrap()
+            .as_any()
+            .downcast_ref::<arrow::array::StructArray>()
+            .unwrap();
+
+        // Extract id and session_id fields from typed_value struct
+        let id_field =
+            ShreddedVariantFieldArray::try_new(typed_value.column_by_name("id").unwrap()).unwrap();
+        let session_id_field =
+            ShreddedVariantFieldArray::try_new(typed_value.column_by_name("session_id").unwrap())
+                .unwrap();
+
+        let id_value = id_field
+            .value_field()
+            .unwrap()
+            .as_any()
+            .downcast_ref::<BinaryViewArray>()
+            .unwrap();
+        let id_typed_value = id_field
+            .typed_value_field()
+            .unwrap()
+            .as_any()
+            .downcast_ref::<FixedSizeBinaryArray>()
+            .unwrap();
+        let session_id_value = session_id_field
+            .value_field()
+            .unwrap()
+            .as_any()
+            .downcast_ref::<BinaryViewArray>()
+            .unwrap();
+        let session_id_typed_value = session_id_field
+            .typed_value_field()
+            .unwrap()
+            .as_any()
+            .downcast_ref::<FixedSizeBinaryArray>()
+            .unwrap();
+
+        // Row 0: Fully shredded - both UUID fields shred successfully
+        assert!(result.is_valid(0));
+
+        assert!(value.is_null(0)); // fully shredded, no remaining fields
+        assert!(id_value.is_null(0));
+        assert!(session_id_value.is_null(0));
+
+        assert!(typed_value.is_valid(0));
+        assert!(id_typed_value.is_valid(0));
+        assert!(session_id_typed_value.is_valid(0));
+
+        assert_eq!(id_typed_value.value(0), mock_uuid_1.as_bytes());
+        assert_eq!(session_id_typed_value.value(0), mock_uuid_2.as_bytes());
+
+        // Row 1: Partially shredded - value contains extra name field
+        assert!(result.is_valid(1));
+
+        assert!(value.is_valid(1)); // contains unshredded "name" field
+        assert!(typed_value.is_valid(1));
+
+        assert!(id_value.is_null(1));
+        assert!(id_typed_value.is_valid(1));
+        assert_eq!(id_typed_value.value(1), mock_uuid_2.as_bytes());
+
+        assert!(session_id_value.is_null(1));
+        assert!(session_id_typed_value.is_valid(1));
+        assert_eq!(session_id_typed_value.value(1), mock_uuid_3.as_bytes());
+
+        // Verify the value field contains the name field
+        let row_1_variant = Variant::new(metadata.value(1), value.value(1));
+        let Variant::Object(obj) = row_1_variant else {
+            panic!("Expected object");
+        };
+
+        assert_eq!(obj.get("name"), Some(Variant::from("test_user")));
+
+        // Row 2: Missing session_id field
+        assert!(result.is_valid(2));
+
+        assert!(value.is_null(2)); // fully shredded, no extra fields
+        assert!(typed_value.is_valid(2));
+
+        assert!(id_value.is_null(2));
+        assert!(id_typed_value.is_valid(2));
+        assert_eq!(id_typed_value.value(2), mock_uuid_1.as_bytes());
+
+        assert!(session_id_value.is_null(2));
+        assert!(session_id_typed_value.is_null(2)); // missing field
+
+        // Row 3: Type mismatch - session_id is a string, not UUID
+        assert!(result.is_valid(3));
+
+        assert!(value.is_null(3)); // no extra fields
+        assert!(typed_value.is_valid(3));
+
+        assert!(id_value.is_null(3));
+        assert!(id_typed_value.is_valid(3));
+        assert_eq!(id_typed_value.value(3), mock_uuid_3.as_bytes());
+
+        assert!(session_id_value.is_valid(3)); // type mismatch, stored in value
+        assert!(session_id_typed_value.is_null(3));
+        let session_id_variant = Variant::new(metadata.value(3), session_id_value.value(3));
+        assert_eq!(session_id_variant, Variant::from("not-a-uuid"));
+
+        // Row 4: Type mismatch - id is int64, not UUID
+        assert!(result.is_valid(4));
+
+        assert!(value.is_null(4)); // no extra fields
+        assert!(typed_value.is_valid(4));
+
+        assert!(id_value.is_valid(4)); // type mismatch, stored in value
+        assert!(id_typed_value.is_null(4));
+        let id_variant = Variant::new(metadata.value(4), id_value.value(4));
+        assert_eq!(id_variant, Variant::from(12345i64));
+
+        assert!(session_id_value.is_null(4));
+        assert!(session_id_typed_value.is_valid(4));
+        assert_eq!(session_id_typed_value.value(4), mock_uuid_1.as_bytes());
+
+        // Row 5: Null
+        assert!(result.is_null(5));
+    }
+
     #[test]
     fn test_spec_compliance() {
         let input = VariantArray::from_iter(vec![Variant::from(42i64), Variant::from("hello")]);