Disable prefetching strictly

Author: Vedin

datafusion/physical-plan/src/joins/grace_hash_join/exec.rs

@@ -1039,7 +1039,7 @@ async fn partition_and_spill_one_side(
             const MAX_TOTAL_TARGET_BUFFER_BYTES: usize = 256 * 1024 * 1024;
             const MIN_FLUSH_BYTES: usize = 1 * 1024 * 1024;
             const MAX_FLUSH_BYTES: usize = 32 * 1024 * 1024;
-            const MAX_SPILL_FILES_PER_SIDE: usize = 128;
+            const MAX_SPILL_FILES_PER_SIDE: usize = 1024;
 
             let total_target_buffer = partition_write_buffer_bytes
                 .clamp(MIN_TOTAL_TARGET_BUFFER_BYTES, MAX_TOTAL_TARGET_BUFFER_BYTES);

datafusion/physical-plan/src/joins/grace_hash_join/stream.rs

@@ -1084,7 +1084,7 @@ impl GraceHashJoinStream {
                                 .adaptive_budget
                                 .current_limit()
                                 .min(PREFETCH_MAX_BYTES);
-                            if estimated_size <= cap {
+                            if PREFETCH_MAX_BYTES > 0 && estimated_size <= cap {
                                 let left_bytes_pf = Arc::new(Mutex::new(0usize));
                                 let right_bytes_pf = Arc::new(Mutex::new(0usize));
                                 let left_fut_pf = load_partition_async(