Composite primary key in django

Question

I have a legacy db table which has composite primary key. I don't think I will be able to change the structure to include a surrogate key, as there is some code written that uses that table. And in django, I cannot use that table, as it doesn't have a primary key(non-composite).

Do django models support composite primary keys? If not, is there any workaround without changing the structure of the table?

P.S. I am using postgresql.

Answer 1

Try similar below code:

class MyTable(models.Model):     class Meta:         unique_together = (('key1', 'key2'),)      key1 = models.IntegerField(primary_key=True)     key2 = models.IntegerField() 

or if you want only unique mixed fields:

class MyTable(models.Model):     class Meta:         unique_together = (('key1', 'key2'),)      key1 = models.IntegerField()     key2 = models.IntegerField() 

EDIT: I would like to note that there is a problem with this approach if there are 3 columns. Update queries don't work because it tries to update (puts pk fields right after "SET") the fields that are unique together and obviously fails.

Answer 2

The accepted answer is fine. However, it's a little old. unique_together may be deprecated in favor of UniqueConstraint. So, the better way of doing this would be;

UniqueConstraint(fields = ['key1', 'key2'], name = 'constraint_name')