From 112b6c40793a18262425ca039e4fe4a6eb68bce4 Mon Sep 17 00:00:00 2001
From: Brion Vibber <brion@pobox.com>
Date: Tue, 12 Oct 2010 16:29:13 -0700
Subject: [PATCH] Improve cache-friendliness of user_group->delete().

Doesn't clear all possible cached entries, but this should get the ones that matter most: lookups by id, nickname, and alias. This should ensure that if a group name gets reused as a new group or alias, it should work properly.
There are some user-visible areas that aren't clear such as the 'top groups' lists on the GroupsAction sidebar; if a deleted group appears in those lists it'll go away within an hour when the cached query expires.
---
 classes/User_group.php | 22 ++++++++++++++++------
 1 file changed, 16 insertions(+), 6 deletions(-)

diff --git a/classes/User_group.php b/classes/User_group.php
index fabb8e8d5c..1f70057852 100644
--- a/classes/User_group.php
+++ b/classes/User_group.php
@@ -551,29 +551,39 @@ class User_group extends Memcached_DataObject
     /**
      * Handle cascading deletion, on the model of notice and profile.
      *
-     * Pretty sure some caching won't get handled properly here.
+     * This should handle freeing up cached entries for the group's
+     * id, nickname, URI, and aliases. There may be other areas that
+     * are not de-cached in the UI, including the sidebar lists on
+     * GroupsAction
      */
     function delete()
     {
         if ($this->id) {
+            // Safe to delete in bulk for now
             $related = array('Group_inbox',
-                             'Group_alias',
                              'Group_block',
                              'Group_member',
-                             'Local_group',
-                             'Related_group',
-                             );
+                             'Related_group');
             Event::handle('UserGroupDeleteRelated', array($this, &$related));
-
             foreach ($related as $cls) {
                 $inst = new $cls();
                 $inst->group_id = $this->id;
                 $inst->delete();
             }
 
+            // And related groups in the other direction...
             $inst = new Related_group();
             $inst->related_group_id = $this->id;
             $inst->delete();
+
+            // Aliases and the local_group entry need to be cleared explicitly
+            // or we'll miss clearing some cache keys; that can make it hard
+            // to create a new group with one of those names or aliases.
+            $this->setAliases(array());
+            $local = Local_group::staticGet('group_id', $this->id);
+            if ($local) {
+                $local->delete();
+            }
         } else {
             common_log(LOG_WARN, "Ambiguous user_group->delete(); skipping related tables.");
         }