Try to fix issues reported by clippy

Author: pwrliang

rust/sedona-spatial-join-gpu/src/stream.rs

@@ -253,8 +253,6 @@ impl GpuSpatialJoinStream {
                     // Execute GPU join with build data
                     match self.execute_gpu_join_with_build_data(&build_data) {
                         Ok(()) => {
-                            let total_result_rows: usize =
-                                self.result_batches.iter().map(|b| b.num_rows()).sum();
                             log::info!(
                                 "GPU join completed, produced {} result batches",
                                 self.result_batches.len()
@@ -342,7 +340,6 @@ impl GpuSpatialJoinStream {
 
         // Concatenate all right batches into one batch
         let _concat_timer = self.join_metrics.concat_time.timer();
-        let concat_start = Instant::now();
         let right_batch = if self.right_batches.len() == 1 {
             self.right_batches[0].clone()
         } else {

rust/sedona-spatial-join-gpu/tests/integration_test.rs

@@ -118,6 +118,7 @@ impl RecordBatchStream for MockStream {
     }
 }
 
+#[cfg(feature = "gpu")]
 #[tokio::test]
 async fn test_gpu_join_exec_creation() {
     // Create simple mock execution plans as children
@@ -151,6 +152,7 @@ async fn test_gpu_join_exec_creation() {
     assert_eq!(gpu_join.children().len(), 2);
 }
 
+#[cfg(feature = "gpu")]
 #[tokio::test]
 async fn test_gpu_join_exec_display() {
     let left_plan = Arc::new(MockExec::new()) as Arc<dyn ExecutionPlan>;
@@ -181,6 +183,7 @@ async fn test_gpu_join_exec_display() {
     assert!(display_str.contains("Inner"));
 }
 
+#[cfg(feature = "gpu")]
 #[tokio::test]
 async fn test_gpu_join_execution_with_fallback() {
     // This test should handle GPU not being available and fallback to CPU error
@@ -250,6 +253,7 @@ async fn test_gpu_join_execution_with_fallback() {
     );
 }
 
+#[cfg(feature = "gpu")]
 #[tokio::test]
 async fn test_gpu_join_with_empty_input() {
     // Test with empty batches (MockExec returns empty stream)