Ticket #10852: 10852_get_page_children.diff

C:/xampp/htdocs/wordpress_trunk/wp-includes/post.php

@@ -2129 +2129 @@
 
 /**
  * Retrieve child pages from list of pages matching page ID.
+ * It returns the entire list of nested descendant pages rooted from page_id
  *
- * Matches against the pages parameter against the page ID. Also matches all
- * children for the same to retrieve all children of a page. Does not make any
- * SQL queries to get the children.
- *
  * @since 1.5.1
  *
  * @param int $page_id Page ID.
  * @param array $pages List of pages' objects.
  * @return array
  */
-function &get_page_children($page_id, $pages) {
-        $page_list = array();
-        foreach ( (array) $pages as $page ) {
-                if ( $page->post_parent == $page_id ) {
-                        $page_list[] = $page;
-                        if ( $children = get_page_children($page->ID, $pages) )
-                                $page_list = array_merge($page_list, $children);
+function &get_page_children( $page_id, &$pages ) {
+        
+        /*
+         * use auxiliary array structure to store the parent-children relations,
+         * which allow O(1) per lookup, and gives O(N) overall complexity
+         * ex: children[10][] contains all the children pages whose parent is 10
+         */
+         $children = array(); 
+         foreach ( (array) $pages as $p ) {
+                
+                $parent_id = intval( $p->post_parent );
+                $children[ $parent_id ][] = $p;
+         }
+         
+         $page_list = array();
+         _page_traverse( $page_id, $children, $page_list );
+         
+        return $page_list;
+}
+
+/**
+ * function to traverse and return all the nested children of a root page.
+ * $children contains parent-chilren relations
+ * 
+ */
+function _page_traverse( $page_id, &$children, &$page_list ){ 
+        
+        if ( isset( $children[ $page_id ] ) ){
+                
+                foreach( (array)$children[ $page_id ] as $child ) {
+                        
+                        $page_list[] = $child; 
+                        _page_traverse( $child->ID, $children, $page_list ); 
                 }
         }
-        return $page_list;
 }
 
 /**