fix: IPC writer should truncate string array with all empty string

arrow/src/ipc/writer.rs

@@ -884,6 +884,16 @@ fn get_buffer_element_width(spec: &BufferSpec) -> usize {
     }
 }
 
+/// Returns byte width for binary value_offset buffer spec.
+#[inline]
+fn get_value_offset_byte_width(data_type: &DataType) -> usize {
+    match data_type {
+        DataType::Binary | DataType::Utf8 => 4,
+        DataType::LargeBinary | DataType::LargeUtf8 => 8,
+        _ => unreachable!(),
+    }
+}
+
 /// Returns the number of total bytes in base binary arrays.
 fn get_binary_buffer_len(array_data: &ArrayData) -> usize {
     if array_data.is_empty() {
@@ -1005,13 +1015,16 @@ fn write_array_data(
         data_type,
         DataType::Binary | DataType::LargeBinary | DataType::Utf8 | DataType::LargeUtf8
     ) {
-        let total_bytes = get_binary_buffer_len(array_data);
-        let value_buffer = &array_data.buffers()[1];
+        let offset_buffer = &array_data.buffers()[0];
+        let value_offset_byte_width = get_value_offset_byte_width(data_type);
+        let min_length = array_data.len() * value_offset_byte_width;
         if buffer_need_truncate(
             array_data.offset(),
-            value_buffer,
-            &BufferSpec::VariableWidth,
-            total_bytes,
+            offset_buffer,
+            &BufferSpec::FixedWidth {
+                byte_width: value_offset_byte_width,
+            },
+            min_length,
         ) {
             // Rebase offsets and truncate values
             let (new_offsets, byte_offset) =
@@ -1029,6 +1042,8 @@ fn write_array_data(
 
             offset = write_buffer(new_offsets.as_slice(), buffers, arrow_data, offset);
 
+            let total_bytes = get_binary_buffer_len(array_data);
+            let value_buffer = &array_data.buffers()[1];
             let buffer_length = min(total_bytes, value_buffer.len() - byte_offset);
             let buffer_slice =
                 &value_buffer.as_slice()[byte_offset..(byte_offset + buffer_length)];
@@ -1832,4 +1847,21 @@ mod tests {
         assert!(structs.column(1).is_null(1));
         assert_eq!(record_batch_slice, deserialized_batch);
     }
+
+    #[test]
+    fn truncate_ipc_string_array_with_all_empty_string() {
+        fn create_batch() -> RecordBatch {
+            let schema = Schema::new(vec![Field::new("a", DataType::Utf8, true)]);
+            let a =
+                StringArray::from(vec![Some(""), Some(""), Some(""), Some(""), Some("")]);
+            RecordBatch::try_new(Arc::new(schema), vec![Arc::new(a)]).unwrap()
+        }
+
+        let record_batch = create_batch();
+        let record_batch_slice = record_batch.slice(0, 1);
+        let deserialized_batch = deserialize(serialize(&record_batch_slice));
+
+        assert!(serialize(&record_batch).len() > serialize(&record_batch_slice).len());
+        assert_eq!(record_batch_slice, deserialized_batch);
+    }
 }