CODEWITHSUNDEEP
djangodjango-models
PawelRoman
PawelRoman

Reputation: 6272

django: iterating over items in ManyToMany table without intermediate model (without using 'through')

I have a simple case with 2 models: Item and Category with ManyToMany between them. I want to show a page listing all categories and for each category list of items. I have hundreds of categories so django hits db hundreds of times (when iterating thru categories and calling items.all() for each one). I need to select data from the intermediate table manually and use select_related() to pull item and category for each record - one query instead of hundreds.

I know that introducing 'through' would solve the problem but I don't want to do it now because it may break existing code (using through makes you can't use add, create, or assignment to create relationships - which I want to avoid for now).

So, is it possible at all without creating a model for intermediate table?

Upvotes: 1

Views: 899

Answers (1)

meshantz
meshantz

Reputation: 1626

You could make a model for your existing table, and just not use it as the through field for the m2m, and make it unmanaged. eg:

class ItemCategory(models.Model):
    item = models.ForeignKey('Item')
    category = models.ForeignKey('Category')

    class Meta:
        db_table = 'the_name_of_the_existing_m2m_table'
        managed = False

Something like that, anyway.

Upvotes: 1

Related Questions