在Django中计算用户等级的最佳方法是什么

Question

I have a web-site written in django. Site have users who have points and a rank according to their points.

class Profile(UserenaBaseProfile):
    points = models.IntegerField(default=100)
    rank = models.PositiveIntegerField(...)

When a user gains a point his/her rank will be changed and so other users as well. The question is what is the best way to calculate rank of the users and when i should calculate or how often?

Thanks.

Answer 1

Probably not the best approach to update the rank of every user each time a single user's points increase. If you have a lot of users this would be harsh on the back end.

If you want to display the users rank on say a profile page perhaps you could have a query that gets a list of all users ordered by points, store this separately as a dictionary or whatever and cache it heavily. This will is better for performance.

so lets say your users list looks like so(the 1111 etc being the usersid):

USERS = { 1111: {'username': 'iskorum', 'points':99999 }, 2222: {'username': 'sidarcy', 'points':9444 }, 3333: {'username': 'joeblogs', 'points':37 } }

When it comes to actually getting the users rank you can simply find the users position in this stored dictionary.

lets say the users id is 1111

userrank = [i+1 for i,x in enumerate(sorted(USERS)) if x == 1111]

returns 1

No extra DB query's needed

If its only a small site no harm getting the user list each time and finding the current users position in that list.

However if your expecting thousands of users the above may be a better approach.

Edit: You should also cache the sorted list, as discussed in the comments below sorting the list each time could eat up a lot of memory