uschindler commented on code in PR #15823:
URL: https://github.com/apache/lucene/pull/15823#discussion_r3010523742


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lucene/core/src/java/org/apache/lucene/util/PriorityQueue.java:
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@@ -174,6 +177,38 @@ public void addAll(Collection<T> elements) {
     }
   }
 
+  /**
+   * Adds all elements of the stream into the queue. This method should be 
preferred over calling
+   * {@link #add(Object)} in loop if all elements are known in advance as it 
builds queue faster.
+   *
+   * <p>If one needs to map or filter element in the iteration of elements in 
this method, call this
+   * method with elements wrapped by {@link Stream#map(Function)} or {@link
+   * Stream#filter(Predicate)}, etc. In these cases, this method should be 
preferred over calling
+   * {@link #addAll(Collection)}.
+   *
+   * <p>If one tries to add more objects than the maxSize passed in the 
constructor, an {@link
+   * ArrayIndexOutOfBoundsException} is thrown. Which may result in parts of 
elements added into the
+   * queue, but the heap is still stay in correct state. In this case, if 
caller wants to readd or
+   * {@link #updateTop(Object)} with remaining elements, it should use a new 
stream, and use {@link
+   * Stream#skip(long)} to skip consumed elements with the delta size of queue.
+   */
+  public void addAll(Stream<T> elements) {
+    // Heap with size S always takes first S elements of the array,
+    // and thus it's safe to fill array further - no actual non-sentinel value 
will be overwritten.
+    try {
+      elements.forEachOrdered(
+          element -> {
+            this.heap[size + 1] = element;
+            this.size++;

Review Comment:
   No there is no concurrency bug lurking here. There is no need to call 
"sequential". I think you have a misunderstanding here. 
   
   The stream itsself will never call the final thing in a concurrent way. The 
implementantion is only required to call the final forEach in correct order, it 
will never be async, so the above code here is semantically corrcet.



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