Error: "there is no unique constraint matching given keys for referenced table" although primary key is included

Question

I am trying to make a comments app for a Django project whereby each record can have a number of comments attached to it. However, when I try to migrate my model, I get the following error:

django.db.utils.ProgrammingError: there is no unique constraint matching given keys for referenced table "user_info"

What am I doing wrong?

Currently my models look like this:

users/models.py

class UserInfo(models.Model):
    id = models.CharField(max_length=25, blank=False, null=False, primary_key=True)
    dob = models.DateField(blank=True, null=True)
    age = models.IntegerField(blank=True, null=True)
    #Includes a number of other fields

    def __str__(self):
        return self.id

    class Meta:
        managed = False
        db_table = 'user_info'
        ordering = ['id']

comments/models.py

from users.models import UserInfo

class Comments(models.Model):
    patient_record = models.ForeignKey(UserInfo, on_delete=models.CASCADE, null=True, blank=True)
    content = models.TextField()
    timestamp = models.DateTimeField(auto_now_add=True)

Answer 1

Just add unique=True to your field and you should be good to go.

class UserInfo(models.Model):
    id = models.CharField(max_length=25, blank=False, null=False, unique=True, primary_key=True)
    dob = models.DateField(blank=True, null=True)
    age = models.IntegerField(blank=True, null=True)
    #Includes a number of other fields

    def __str__(self):
        return self.id

    class Meta:
        managed = False
        db_table = 'user_info'
        ordering = ['id']

The primary key needs to be unique to work. If not, you can simply have made two UserInfo entries with the same id , rendering the PK useless. On a separate note, why are you using your own id field instead of the one already provided by Django?