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
14290	Rendering is very inefficient when USE_L10N. Caching format values gives 2-7 times improvement	Teemu Kurppa	Jannis Leidel	"Django's rendering is really inefficient if localization is turned on (USE_L10N = True).  

I have a spreadsheet like view with a few thousand numbers, dates and related data and it spend almost all of it's time in template rendering even when I preprocessed data carefully.
I investigated the issue and it seems that Django's localization implementation is doing a lot of unnecessary work for every rendered number, date and time. 

Following patch introduces caching of locale-specific format values.

Speed improvements are considerable. On my laptop and our server, this gives '''5-7 times improvement''' (from ~5 sec to <1sec) to rendering speed of an anomalistic view with 10000 integers. For my real-world spreadsheet view, the whole processing time of Django improves  2-3 times (from ~2sec to ~0.8sec) 

In addition to the patch, I've included a test project, which can be used to test observe and test the problem.

Run test to see raw rendering performance
{{{
python manage.py test numbersperf
}}}

And to test it with server try
{{{
python manage.py runserver 
}}}
And then visit these urls to observe and profile the problem
{{{
http://localhost:8000/test/10000
http://localhost:8000/test/10000?timing
http://localhost:8000/test/10000?prof
}}}
"		closed	Internationalization	dev		fixed	localization, rendering,		Accepted	1	1	1	0	0	0