Re: Url regex keeps django busy/crashing

On 26-7-2012 16:45, Joe wrote:
> Hey, I have a url regex like this which is keeping django extremely busy
> (20secs to 1min to handle a request). On some urls it even crashes.
>
> my regex:
>
> url(r'^(?P<item_url>(\w+-?)*)/$', 'detail'),

Turn the * into a + and you'll see great improvements and I also think
you don't want to match '//' as a valid URL part.
Also, I think this example will satisfy your requirements in practice:

url(r'^(?P<item_url>\w[\w-]+-/$', 'detail')

The only difference is that dashes are allowed to follow each other. I
can only think of one valid reason to not use the above URL and that is
if "multiple dashes" are captured in another URL.
Remember that URL patterns are not your validators. It's nice if you can
prevent a view from being called by carefully constructing your URL
patterns, but if parsing the regex takes longer then calling the view
you loose performance instead.
Also, validating if a URL contains two or more consecutive dashes is
easily done in a view and does not even need regular expressions:
def detail(request, item_url) :
if '--' in item_url :
raise 404

Even more improvements if you keep the urls lower case (or uppercase,
but not mixed case) and use [a-z0-9_] instead of \w.
--
Melvyn Sopacua

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