Fixed #5267 -- Documented that order_by('?') queries can be slow
Fixed #5267 -- Documented that order_by('?') queries can be slow

git-svn-id: 4f9f921b081c523744c7bf24d959a0db39629563@6293 bcc190cf-cafb-0310-a4f2-bffc1f526a37

Smarsh/django,dcramer/django-compositepks,Instagram/django,jamespacileo/django-france,Smarsh/django,alex/django-old,dcramer/django-compositepks,bfirsh/django-old,disqus/django-old,disqus/django-old,django-nonrel/django-nonrel,hugs/django,django-nonrel/django-nonrel,alex/django-old,hugs/django,sam-tsai/django-old,sam-tsai/django-old,t11e/django,Instagram/django,sam-tsai/django-old,skevy/django,skevy/django,mitsuhiko/django,disqus/django-old,Smarsh/django,django-nonrel/django-nonrel,dcramer/django-compositepks,t11e/django,jamespacileo/django-france,mitsuhiko/django,bfirsh/django-old,skevy/django,mitsuhiko/django,sam-tsai/django-old,hugs/django,bfirsh/django-old,t11e/django,jamespacileo/django-france,Smarsh/django,Instagram/django,alex/django-old