From e382e83a35e9b2932c1cc1c6194a6fcd8ceaa831 Mon Sep 17 00:00:00 2001
From: Xuanwo <github@xuanwo.io>
Date: Tue, 2 Dec 2025 19:14:40 +0800
Subject: [PATCH 1/2] chore: add a test case for variable packed struct

Signed-off-by: Xuanwo <github@xuanwo.io>
---
 .../src/encodings/physical/packed.rs          | 38 +++++++++++++++++++
 1 file changed, 38 insertions(+)

diff --git a/rust/lance-encoding/src/encodings/physical/packed.rs b/rust/lance-encoding/src/encodings/physical/packed.rs
index 88f31be412e..29c33df6a95 100644
--- a/rust/lance-encoding/src/encodings/physical/packed.rs
+++ b/rust/lance-encoding/src/encodings/physical/packed.rs
@@ -735,13 +735,17 @@ mod tests {
     use crate::{
         compression::CompressionStrategy,
         compression::{DefaultCompressionStrategy, DefaultDecompressionStrategy},
+        constants::PACKED_STRUCT_META_KEY,
         statistics::ComputeStat,
+        testing::{check_round_trip_encoding_of_data, TestCases},
         version::LanceFileVersion,
     };
     use arrow_array::{
         Array, ArrayRef, BinaryArray, Int32Array, Int64Array, LargeStringArray, StringArray,
+        StructArray, UInt32Array,
     };
     use arrow_schema::{DataType, Field as ArrowField, Fields};
+    use std::collections::HashMap;
     use std::sync::Arc;
 
     fn fixed_block_from_array(array: Int64Array) -> FixedWidthDataBlock {
@@ -947,6 +951,40 @@ mod tests {
         Ok(())
     }
 
+    #[tokio::test]
+    async fn variable_packed_struct_utf8_round_trip() {
+        // schema: Struct<id: UInt32, uri: Utf8>
+        let fields = Fields::from(vec![
+            Arc::new(ArrowField::new("id", DataType::UInt32, false)),
+            Arc::new(ArrowField::new("uri", DataType::Utf8, false)),
+        ]);
+
+        // mark struct as packed
+        let mut meta = HashMap::new();
+        meta.insert(PACKED_STRUCT_META_KEY.to_string(), "true".to_string());
+
+        let array = Arc::new(StructArray::from(vec![
+            (
+                fields[0].clone(),
+                Arc::new(UInt32Array::from(vec![1, 2, 3])) as ArrayRef,
+            ),
+            (
+                fields[1].clone(),
+                Arc::new(StringArray::from(vec![
+                    Some("a"),
+                    Some("b"),
+                    Some("/tmp/x"),
+                ])) as ArrayRef,
+            ),
+        ]));
+
+        let test_cases = TestCases::default()
+            .with_min_file_version(LanceFileVersion::V2_2)
+            .with_expected_encoding("variable_packed_struct");
+
+        check_round_trip_encoding_of_data(vec![array], &test_cases, meta).await;
+    }
+
     #[test]
     fn variable_packed_struct_multi_variable_round_trip() -> Result<()> {
         let arrow_fields: Fields = vec![

From 2c9c4e3fda6778e3d36c28713f262b415875d231 Mon Sep 17 00:00:00 2001
From: Xuanwo <github@xuanwo.io>
Date: Fri, 5 Dec 2025 16:52:15 +0800
Subject: [PATCH 2/2] Polish tests

Signed-off-by: Xuanwo <github@xuanwo.io>
---
 rust/lance-encoding/src/encodings/physical/packed.rs | 11 ++++++++++-
 1 file changed, 10 insertions(+), 1 deletion(-)

diff --git a/rust/lance-encoding/src/encodings/physical/packed.rs b/rust/lance-encoding/src/encodings/physical/packed.rs
index 29c33df6a95..31ce7acd1e4 100644
--- a/rust/lance-encoding/src/encodings/physical/packed.rs
+++ b/rust/lance-encoding/src/encodings/physical/packed.rs
@@ -953,10 +953,11 @@ mod tests {
 
     #[tokio::test]
     async fn variable_packed_struct_utf8_round_trip() {
-        // schema: Struct<id: UInt32, uri: Utf8>
+        // schema: Struct<id: UInt32, uri: Utf8, long_text: LargeUtf8>
         let fields = Fields::from(vec![
             Arc::new(ArrowField::new("id", DataType::UInt32, false)),
             Arc::new(ArrowField::new("uri", DataType::Utf8, false)),
+            Arc::new(ArrowField::new("long_text", DataType::LargeUtf8, false)),
         ]);
 
         // mark struct as packed
@@ -976,6 +977,14 @@ mod tests {
                     Some("/tmp/x"),
                 ])) as ArrayRef,
             ),
+            (
+                fields[2].clone(),
+                Arc::new(LargeStringArray::from(vec![
+                    Some("alpha"),
+                    Some("a considerably longer payload for testing"),
+                    Some("mid"),
+                ])) as ArrayRef,
+            ),
         ]));
 
         let test_cases = TestCases::default()