Customizing Incremental Primary Keys with Prefixes and Suffixes in Django

Posted on Views: Waline: Word count in article: 291 Reading time ≈ 1 mins.
The project requirement was to use a prefixed incremental primary key in Django's model, which should be globally unique. The author shares the implementation method, creating a separate model to ensure the uniqueness of the incremental number, defining a character primary key in the business model and modifying the save method to add a prefix, and also provides sample code.

Recently, a requirement emerged in the project. In Django’s model, the primary key needed to be an incremental type with a prefix, like: exp-1, exp-2… and so on. Moreover, across all models, the incremental data within the primary key had to be unique, without any duplicates. That is, if there are two models A and B, once exp-1 is used in A, it is not allowed to be used in B. After searching online, I couldn’t find a particularly good implementation method, so I wrote one myself and am making a record here.

The method I adopted is actually quite simple:

  1. Create a separate model with only one field of the models.AutoField type, which can ensure that the incremental number in the primary key is globally unique.
  2. Define a primary key of the models.CharFiled type in the actual business model.
  3. Modify the save method to add a prefix to the primary key of the business model.

Here is the sample code for reference:

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from django.db import models


class AutoIncrementFields(models.Model):
    """
    provide a unique ID for all models of code sign
    """
    id = models.AutoField(primary_key=True)
    def __str__(self):
        return str(self.id)


class A(models.Model):
    """
    example
    """
    case_id = models.CharField(max_length=128, primary_key=True)  # custom save func will cover this field
    
    def save(self, *args, **kwargs):
        """
        customize primary key like exp-1, exp-2...
        :param args:
        :param kwargs:
        :return:
        """
        _ = AutoIncrementFields.objects.create()
        self.case_id = 'exp-' + str(_.id)
        return super(A, self).save(*args, **kwargs)


class B(models.Model):
    """
    example
    """
    case_id = models.CharField(max_length=128, primary_key=True)  # custom save func will cover this field
    
    def save(self, *args, **kwargs):
        """
        customize primary key like exp-1, exp-2...
        :param args:
        :param kwargs:
        :return:
        """
        _ = AutoIncrementFields.objects.create()
        self.case_id = 'exp-' + str(_.id)
        return super(B, self).save(*args, **kwargs)