old_contents: from django.contrib import admin
  
  from registration.models import RegistrationProfile
  
  
  class RegistrationAdmin(admin.ModelAdmin):
      list_display = ('__unicode__', 'activation_key_expired')
      search_fields = ('user__username', 'user__first_name')
  
  
  admin.site.register(RegistrationProfile, RegistrationAdmin)
  
new_contents: from django.contrib import admin
  
  from registration.models import RegistrationProfile
  
  
  class RegistrationAdmin(admin.ModelAdmin):
      list_display = ('__unicode__', 'activation_key_expired')
      raw_id_fields = ['user']
      search_fields = ('user__username', 'user__first_name')
  
  
  admin.site.register(RegistrationProfile, RegistrationAdmin)
  
subject: Use raw_id_fields for the relation from RegistrationProfile to User, for sites which have huge numbers of users.