Trac fetches entire permissions table several times during request

[jdorn@…]

We've found trac fetching the entire contents of the permission table one time for each user in the database on every request. This was slowing down our instance considerably.

Here is a patch fixing this issue:

Index: trac/perm.py
===================================================================
--- trac/perm.py        (revision 11167)
+++ trac/perm.py        (working copy)
@@ -156,7 +156,7 @@
     permissions and groups.
     """
     implements(IPermissionStore)
-
+    _user_perms = None
     group_providers = ExtensionPoint(IPermissionGroupProvider)
 
     def get_user_permissions(self, username):
@@ -174,9 +174,11 @@
 
         actions = set([])
         db = self.env.get_db_cnx()
-        cursor = db.cursor()
-        cursor.execute("SELECT username,action FROM permission")
-        rows = cursor.fetchall()
+        if (self._user_perms == None):
+            cursor = db.cursor()
+            cursor.execute("SELECT username,action FROM permission")
+            self._user_perms = cursor.fetchall()
+        rows = self._user_perms
         while True:
             num_users = len(subjects)
             num_actions = len(actions)

[Remy Blank]

This has been fixed in [11032], as part of #4245.