Skip unnecessary plan rebuild in adjust_input_keys_ordering

When a plan node has no join/aggregate key reordering requirements
(requirements.data is empty) and falls through to the default else
branch, adjust_input_keys_ordering previously returned Transformed::yes
unconditionally. This triggered with_new_children rebuilds on every
node in the tree, even though nothing changed.

Add an early return with Transformed::no when requirements.data is
empty, avoiding unnecessary plan tree rebuilds for non-join plans.

Author: zhuqi-lucas

Cargo.lock

@@ -3978,3 +3978,33 @@ fn maintains_order_preserves_spm_through_union_with_prefer_existing_sort() -> Re
 
     Ok(())
 }
+
+/// Verifies that `adjust_input_keys_ordering` returns `Transformed::no`
+/// for a simple scan plan with no key requirements, avoiding an
+/// unnecessary plan rebuild.
+#[test]
+fn adjust_input_keys_ordering_no_transform_for_scan() -> Result<()> {
+    let plan: Arc<dyn ExecutionPlan> = parquet_exec();
+    let requirements = PlanWithKeyRequirements::new_default(plan);
+    let result = adjust_input_keys_ordering(requirements)?;
+    assert!(
+        !result.transformed,
+        "expected Transformed::no for a scan plan with empty requirements"
+    );
+    Ok(())
+}
+
+/// Verifies that `adjust_input_keys_ordering` applied via `transform_down`
+/// over a filter -> scan tree returns `Transformed::no` when there are no
+/// join/aggregate key requirements.
+#[test]
+fn adjust_input_keys_ordering_no_transform_for_filter_scan() -> Result<()> {
+    let plan: Arc<dyn ExecutionPlan> = filter_exec(parquet_exec());
+    let requirements = PlanWithKeyRequirements::new_default(plan);
+    let result = requirements.transform_down(adjust_input_keys_ordering)?;
+    assert!(
+        !result.transformed,
+        "expected Transformed::no for a filter->scan tree with no key requirements"
+    );
+    Ok(())
+}

datafusion/core/tests/physical_optimizer/enforce_distribution.rs

@@ -412,6 +412,9 @@ pub fn adjust_input_keys_ordering(
         || plan.is::<WindowAggExec>()
     {
         requirements.data.clear();
+    } else if requirements.data.is_empty() {
+        // No requirements to push down and no plan changes — skip rebuild.
+        return Ok(Transformed::no(requirements));
     } else {
         // By default, push down the parent requirements to children
         for child in requirements.children.iter_mut() {