Django Admin ManyToMAny Behaviour

In that post want to share an experience with a Django behaviour that took all my day to solve it. In nowadays , i'm working on a freelance project and trying to finish project due to deadline (hate deadlines). Here is the small part of models i'm using

class SchoolSection(models.Model):
 #snip

class GalleryItem(models.Model):
 school_section = models.ManyToManyField(SchoolSection)
 #snip

A pretty easy structure , the problem occurred when i connected the post_save signal to a method which was using the models above. When a new GalleryItem was saved i wanted to pre-populate some xml files according to new commers. Here is the simple code that was pulling the gallery items :

sc=SchoolSection.objects.all()
gi = GalleryItem.objects.filter(school_section = sc[0])

When i save an object i was not able to see the new added in query above. When i saved the object second time (edit->save) the new entry appeared. In a moment when i was going go crazy someone from #django channel told me that Django doesnt save the m2m relationships immediately due to performance issues. Therefore the solution was to override a method in admin part , here is the solution :

class GalleryItemAdmin(admin.ModelAdmin):
 def save_model(self, request, obj, form, change):
   super(GalleryItemAdmin, self).save_model(request, obj, form, change)
   form.save_m2m()
   obj.save()

That is all, hope to help someone who has the same problem :)