Django: Best way for simple hierarchy?

Question

I have this model:

class Category(models.Model):
    name = models.CharField()
    description = models.CharField(blank=True)
    parent = models.ForeignKey('self', blank=True, null=True)

I want Django to sort the categories with respect to their hierarchy, for example:

Parent 1
- Child 1
Parent 2
- Child 1

I did some research and found 2 apps, treebeard.al_tree and Django MPTT, both are powerful which may lead to lower performance or harder to maintain.

I will display the categories in website's sidebar and inside admin pages (includes ForeignKey in posts model), there will be very low additions/modifications/deletions to categories, mostly reading only which should have no big affect on performance.

Is there any other app which offers this and simpler than those above? Can I achieve this using Django without additional apps, using managers or something else?

Even if you do not use MPTT, you can have some idea of how it works by looking into its code. — Ankit Jaiswal, Dec 02 '10 at 11:17

score 4 · Accepted Answer · answered Dec 02 '10 at 11:17

4

I do not see any disadvantes using an app like django-mptt. In fact the methods provided by it are optimized to give you a maximum in performance when doing queries with hierarchical structures. No reason for me to worry about maintainability and/or performance and it is quite easy to use!

answered Dec 02 '10 at 11:17

Bernhard Vallant

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Thanks, I will use django-mptt. – Someone Dec 02 '10 at 11:52

score 4 · Answer 2 · answered Dec 02 '10 at 11:19

4

MPTT or treebeard may lead to lower performance? Nonsense. The whole point of these apps is that they provide highly optimised algorithms that massively increase performance. MPTT allows you to grab whole trees or sub-sections of them with a single database operation, which would otherwise need many separate calls.

answered Dec 02 '10 at 11:19

Daniel Roseman

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My point was that a big app with many options may be slower than a simpler one with specific needs. I will use django-mptt now. Thanks. – Someone Dec 02 '10 at 11:53

score 2 · Answer 3 · answered Dec 02 '10 at 11:21

Using MPTT is there to make the system perform. When you implement it yourself, you may end up connecting the nodes together manually (a ~30 line function), or doing individual queries for all sublevels. Lots of manual work, been there, done that.

With the MPTT algorithm, a subtree can be fetched in one query. It's a common algorithm to store hierarchical data.

Django MPTT (especially v0.4) has some nice API's to display all this data properly in the admin and templates. You don't have to reinvent the wheel.

Thanks, I will use django-mptt. – Someone Dec 02 '10 at 11:54 — Someone, Dec 02 '10 at 11:54

Django: Best way for simple hierarchy?

3 Answers3