Function binaryheap_remove_first

src/backend/lib/binaryheap.c:173–194

* binaryheap_remove_first * * Removes the first (root, topmost) node in the heap and returns a * pointer to it after rebalancing the heap. The caller must ensure * that this routine is not used on an empty heap. O(log n) worst * case. */

 * case.
 */
Datum
binaryheap_remove_first(binaryheap *heap)
{
	Assert(!binaryheap_empty(heap) && heap->bh_has_heap_property);

	if (heap->bh_size == 1)
	{
		heap->bh_size--;
		return heap->bh_nodes[0];
	}

	/*
	 * Swap the root and last nodes, decrease the size of the heap (i.e.
	 * remove the former root node) and sift the new root node down to its
	 * correct position.
	 */
	swap_nodes(heap, 0, heap->bh_size - 1);
	heap->bh_size--;
	sift_down(heap, 0);

	return heap->bh_nodes[heap->bh_size];
}

/*
 * binaryheap_replace_first