chore: tweak batch deletion concurrency (#16770)

* chore: tweak batch deletion concurrency

* chore: tweak remove file in batch thread pool size

src/query/storages/common/io/src/files.rs

@@ -68,10 +68,15 @@ impl Files {
                     .map(|location| Self::delete_files(self.operator.clone(), location.to_vec()))
             });
 
+            // At most 3 concurrent batch deletions allowed, mitigate rate limit errors
+            let permit = (threads_nums / 2).clamp(1, 3);
+
+            // IO tasks, 2 threads should be enough
+            let pool_thread_number = 2;
             execute_futures_in_parallel(
                 tasks,
-                threads_nums,
-                threads_nums * 2,
+                pool_thread_number,
+                permit,
                 "batch-remove-files-worker".to_owned(),
             )
             .await?