id	summary	reporter	owner	description	type	status	component	version	severity	resolution	keywords	cc	stage	has_patch	needs_docs	needs_tests	needs_better_patch	easy	ui_ux
18676	Django should do m2m deletes in a single query when possible	Jeremy Dunck	nobody	"https://groups.google.com/forum/?fromgroups#!topic/django-developers/zoS8gAyZWjI

As Anssi notes there: 
{{{
To me it seems there is no reason to do two queries in delete if the
following conditions hold:
  - there are no signals sent for the deleted objects
  - the delete does not cascade further (actually you don't need to
collect even in this case - you can do the cascade query completely in
the DB without fetching the IDs first).
}}}

I think a good first-cut is auto-created intermediate table and no signals attached for that model.

"	Cleanup/optimization	closed	Database layer (models, ORM)	1.4	Normal	fixed		django@…	Ready for checkin	1	0	0	0	0	0