protected Map<String, Object> saveTransientDescendantComponentStates(FacesContext facesContext, Map<String, Object> childStates, Iterator<UIComponent> childIterator,
            boolean saveChildFacets)
    {
        while (childIterator.hasNext())
        {
            UIComponent child = childIterator.next();
            if (!child.isTransient())
            {
                Iterator<UIComponent> childsIterator;
                if (saveChildFacets)
                {
                    childsIterator = child.getFacetsAndChildren();
                }
                else
                {
                    childsIterator = child.getChildren().iterator();
                }
                childStates = saveTransientDescendantComponentStates(facesContext, childStates, childsIterator, true);
                Object state = child.saveTransientState(facesContext);
                if (state != null)
                {
                    if (childStates == null)
                    {
                        childStates = new HashMap<>();
                    }
                    childStates.put(child.getClientId(facesContext), state);
                }
            }
        }
        return childStates;
    }
<p class="changed_added_2_1">Override the base class method to
take special action if the method is being invoked when {@link
StateManager#IS_BUILDING_INITIAL_STATE} is true
<strong>and</strong> the <code>rowStatePreserved</code>
JavaBeans property for this instance is <code>true</code>.</p>

<p class="changed_modified_2_1">The additional action taken is to
traverse the descendents and save their state without regard to
any particular row value.</p>

@since 2.1
primefaces/src/main/java/org/primefaces/component/patch/UIDataPatch.java