3 files changed, 21 insertions, 9 deletions
diff --git a/phpBB/includes/nestedset/base.php b/phpBB/includes/nestedset/base.php
index 9f83bd757c..1a6b578e79 100644
--- a/phpBB/includes/nestedset/base.php
+++ b/phpBB/includes/nestedset/base.php
@@ -674,7 +674,7 @@ abstract class phpbb_nestedset_base implements phpbb_nestedset_interface
 	/**
 	* @inheritdoc
 	*/
-	public function recalculate_nested_set($new_id, $parent_id = 0, $reset_ids = false)
+	public function regenerate_left_right_ids($new_id, $parent_id = 0, $reset_ids = false)
 	{
 		if ($reset_ids)
 		{
@@ -716,7 +716,7 @@ abstract class phpbb_nestedset_base implements phpbb_nestedset_interface
 			$new_id++;
 
 			// Then we go through any children and update their left/right id's
-			$new_id = $this->recalculate_nested_set($new_id, $row[$this->column_item_id]);
+			$new_id = $this->regenerate_left_right_ids($new_id, $row[$this->column_item_id]);
 
 			// Then we come back and update the right_id for this module
 			if ($row[$this->column_right_id] != $new_id)
diff --git a/phpBB/includes/nestedset/interface.php b/phpBB/includes/nestedset/interface.php
index b8a2e4b239..9948ccf019 100644
--- a/phpBB/includes/nestedset/interface.php
+++ b/phpBB/includes/nestedset/interface.php
@@ -124,12 +124,24 @@ interface phpbb_nestedset_interface
 	public function get_parent_data(array $item);
 
 	/**
-	* Recalculate Nested Sets
+	* Regenerate left/right ids from parent/child relationship
+	*
+	* This method regenerates the left/right ids for the nested set based on
+	* the parent/child relations. This function executes three queries per
+	* item, so it should only be called, when the set has one of the following
+	* problems:
+	*	- The set has a duplicated value inside the left/right id chain
+	*	- The set has a missing value inside the left/right id chain
+	*	- The set has items that do not have a left/right is set
+	*
+	* When regenerating the items, the items are sorted by parent id and their
+	* current left id, so the current child/parent relationships are kept
+	* and running the function on a working set will not change any orders.
 	*
 	* @param int	$new_id		First left_id to be used (should start with 1)
 	* @param int	$parent_id	parent_id of the current set (default = 0)
 	* @param bool	$reset_ids	Should we reset all left_id/right_id on the first call?
 	* @return	int		$new_id		The next left_id/right_id that should be used
 	*/
-	public function recalculate_nested_set($new_id, $parent_id = 0, $reset_ids = false);
+	public function regenerate_left_right_ids($new_id, $parent_id = 0, $reset_ids = false);
 }
diff --git a/tests/nestedset/set_forum_recalculate_test.php b/tests/nestedset/set_forum_regenerate_test.php
index 6ff7a372a4..0e3a2123a0 100644
--- a/tests/nestedset/set_forum_recalculate_test.php
+++ b/tests/nestedset/set_forum_regenerate_test.php
@@ -9,7 +9,7 @@
 
 require_once dirname(__FILE__) . '/set_forum_base.php';
 
-class phpbb_tests_nestedset_set_forum_recalculate_test extends phpbb_tests_nestedset_set_forum_base
+class phpbb_tests_nestedset_set_forum_regenerate_test extends phpbb_tests_nestedset_set_forum_base
 {
 	protected $fixed_set = array(
 		array('forum_id' => 1, 'parent_id' => 0, 'left_id' => 1, 'right_id' => 6, 'forum_parents' => ''),
@@ -27,7 +27,7 @@ class phpbb_tests_nestedset_set_forum_recalculate_test extends phpbb_tests_neste
 		array('forum_id' => 11, 'parent_id' => 7, 'left_id' => 20, 'right_id' => 21, 'forum_parents' => ''),
 	);
 
-	public function recalculate_nested_set_data()
+	public function regenerate_left_right_ids_data()
 	{
 		return array(
 			array('UPDATE phpbb_forums
@@ -56,13 +56,13 @@ class phpbb_tests_nestedset_set_forum_recalculate_test extends phpbb_tests_neste
 	}
 
 	/**
-	* @dataProvider recalculate_nested_set_data
+	* @dataProvider regenerate_left_right_ids_data
 	*/
-	public function test_recalculate_nested_set($breaking_query, $reset_ids)
+	public function test_regenerate_left_right_ids($breaking_query, $reset_ids)
 	{
 		$result = $this->db->sql_query($breaking_query);
 
-		$this->assertEquals(23, $this->set->recalculate_nested_set(1, 0, $reset_ids));
+		$this->assertEquals(23, $this->set->regenerate_left_right_ids(1, 0, $reset_ids));
 
 		$result = $this->db->sql_query('SELECT forum_id, parent_id, left_id, right_id, forum_parents
 			FROM phpbb_forums