From 02e07c0e851b001badbe491405e86bfca6733cb1 Mon Sep 17 00:00:00 2001
From: Helmut Merz <helmutm@cy55.de>
Date: Mon, 21 Nov 2011 12:35:07 +0100
Subject: [PATCH] performance improvement: only create new relation if
 necessary, simplified

---
 common.py | 11 ++++++-----
 1 file changed, 6 insertions(+), 5 deletions(-)

diff --git a/common.py b/common.py
index 602c581..293885c 100644
--- a/common.py
+++ b/common.py
@@ -482,13 +482,14 @@ class ParentRelation(object):
         return None
 
     def __set__(self, inst, value):
-        s = ParentRelationSet(inst, self.predicateName)
-        for current in s:
+        rs = ParentRelationSet(inst, self.predicateName)
+        rsList = list(rs)
+        for current in rsList:
             if current != value:
-                s.remove(current)
+                rs.remove(current)
         if value is not None:
-            if value not in s:
-                s.add(value)    # how to supply additional parameters?
+            if value not in rsList:
+                rs.add(value)    # how to supply additional parameters?
 
 
 # caching (TBD)