Ticket #1334: magic_removal-manytomany_save_fix.diff

db/models/manipulators.py

@@ -8 +8 @@
 from django.utils.datastructures import DotExpandedDict, MultiValueDict
 import types
 
+# For Python 2.3
+if not hasattr(__builtins__, 'set'):
+    from sets import Set as set
+
 def add_manipulators(sender):
     cls = sender
     cls.add_to_class('AddManipulator', AutomaticAddManipulator)
@@ -119 +123 @@
                         new_vals = new_data.get(f.name, ())
                     else:
                         new_vals = new_data.getlist(f.name)
-                    was_changed = getattr(new_object, 'set_%s' % f.name)(new_vals)
-                    if self.change and was_changed:
+                    try:
+                        new_vals = [int(x) for x in new_vals]
+                    except ValueError:
+                        pass
+                    rel_manager = getattr(new_object, f.name)
+                    prev_vals = [x._get_pk_val() for x in rel_manager.all()]
+                    prev_val_set = set(prev_vals)
+                    new_val_set = set(new_vals)
+                    if self.change and prev_val_set != new_val_set:
+                        remove_val_set = prev_val_set - new_val_set
+                        add_val_set = new_val_set - prev_val_set
+                        if remove_val_set:
+                            rel_manager.remove(*rel_manager.model.objects.filter(id__in=remove_val_set))
+                        if add_val_set:
+                            rel_manager.add(*rel_manager.model.objects.filter(id__in=add_val_set))
                         self.fields_changed.append(f.verbose_name)
 
         expanded_data = DotExpandedDict(dict(new_data))

db/models/fields/related.py

@@ -127 +127 @@
         (rel_col_name, join_table, this_col_name,
         rel_col_name, ",".join(['%s'] * len(new_ids))), 
         [this_pk_val] + list(new_ids))
-    existing_ids = set([row[0] for row in cursor.fetchmany(rowcount)])
+    if rowcount:
+        existing_ids = set([row[0] for row in cursor.fetchmany(rowcount)])
+    else:
+        existing_ids = set()
 
     # Add the ones that aren't there already
     for obj_id in (new_ids - existing_ids):