CODEWITHSUNDEEP
djangodjango-modelsforeign-keysprimary-key
dialex
dialex

Reputation: 2876

Tell Django's model to use as primary key a set of foreign keys

I have Persons and Proposals. Now I want to store the Person's votes on Proposals. To do so, I'll create another class which will provide an "intermediary" table. The goal is to link a Person with a Proposal and associate a vote direction (upvote or downvote). Code below:

class Persons(models.Model):
   #code
class Proposal(models.Model):
   #code
class Vote(models.Model):
    """A Person (who) votes up or down (direction) a Proposal (what)."""
    who = models.ForeignKey(Person)
    what = models.ForeignKey(Proposal)
    direction = models.BooleanField()   # true = upvote = vote in favor

I wanted the PrimaryKey of Vote to be (who, what) together. Instead, Django created a table with an default AUTO-INCREMENTED id as PrimaryKey. How can I set a ForeignKey (or a set of ForeignKeys) as PrimaryKey?

Upvotes: 1

Views: 3683

Answers (3)

vaibhav
vaibhav

Reputation: 51

I too had a similar problem and i was able to work around it by using unique_together meta (in your case under class Vote). read more about unique_together at

https://docs.djangoproject.com/en/dev/ref/models/options/

Upvotes: 4

Chris Hawkes
Chris Hawkes

Reputation: 12420

unfortunately you may be stuck using SQLAlchemy since the standard ORM is not capable of this.

Upvotes: 3

Brandon Taylor
Brandon Taylor

Reputation: 34573

Django ORM does not support composite primary keys: https://code.djangoproject.com/wiki/MultipleColumnPrimaryKeys

Upvotes: 4

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