Revise the Performance section in topics/http/urls

[Tzu-ping Chung]

The section, written back in the 0.9 days during 2005, goes:

Each regular expression in a urlpatterns is compiled the first time it’s accessed. This makes the system blazingly fast.

​https://docs.djangoproject.com/en/dev/topics/http/urls/#performance

While the first part of the sentence is true, it does not serve as a reason why the dispatcher is blazingly fast. And the general public perception these days is almost the opposite: Django’s URL dispatcher is thought to be between “not fast” and “slow”, depending on what standard you compare it against.

While I am happy with Django’s URL dispatcher, and certainly don’t have anything to complain, it might be a good idea to remove the ten-year-old statement that is not valid anymore.

[Tim Graham]

I'd suggest to revise the section to describe what parts of the URL system are fast (routing URLs, I think) and what parts are slow (reversing URLs, I think). There are probably other considerations. Marten might be in a good position to do this since he's been working on some ​URL dispatcher changes.

[j-shu]

PR on: ​https://github.com/django/django/pull/6879

[Tim Graham]

Comments for improvement are on the PR.