upd

Author: idegtiarenko

x-pack/plugin/esql-core/src/main/java/org/elasticsearch/xpack/esql/core/tree/Node.java

@@ -67,8 +67,8 @@ public List<T> children() {
     @SuppressWarnings("unchecked")
     public void forEachDown(Consumer<? super T> action) {
         action.accept((T) this);
-        // please do not refactor it to a for-each loop
-        // to avoid allocating iterator that performs concurrent modification checks
+        // please do not refactor it to a for-each loop to avoid
+        // allocating iterator that performs concurrent modification checks and extra stack traces
         for (int c = 0, size = children.size(); c < size; c++) {
             children.get(c).forEachDown(action);
         }
@@ -85,8 +85,8 @@ public <E extends T> void forEachDown(Class<E> typeToken, Consumer<? super E> ac
 
     @SuppressWarnings("unchecked")
     public void forEachUp(Consumer<? super T> action) {
-        // please do not refactor it to a for-each loop
-        // to avoid allocating iterator that performs concurrent modification checks
+        // please do not refactor it to a for-each loop to avoid
+        // allocating iterator that performs concurrent modification checks and extra stack traces
         for (int c = 0, size = children.size(); c < size; c++) {
             children.get(c).forEachUp(action);
         }

x-pack/plugin/esql/src/main/java/org/elasticsearch/xpack/esql/plan/QueryPlan.java

@@ -144,8 +144,8 @@ private static Object doTransformExpression(Object arg, Function<Expression, ? e
         if (arg instanceof List<?> c) {
             List<Object> transformed = null;
             boolean hasChanged = false;
-            // please do not refactor it to a for-each loop
-            // to avoid allocating iterator that performs concurrent modification checks
+            // please do not refactor it to a for-each loop to avoid
+            // allocating iterator that performs concurrent modification checks and extra stack traces
             for (int i = 0, size = c.size(); i < size; i++) {
                 var e = c.get(i);
                 Object next = doTransformExpression(e, traversal);
@@ -160,7 +160,7 @@ private static Object doTransformExpression(Object arg, Function<Expression, ? e
 
             return hasChanged ? transformed : arg;
         }
-        assert arg instanceof Set<?> == false : "Set arguments are not supported";
+        assert arg instanceof Collection<?> == false : "Non-List Collection implementations are not supported";
 
         return arg;
     }