CODEWITHSUNDEEP
djangodjango-models
Rahul Sharma
Rahul Sharma

Reputation: 2495

Add a prefix to primary key in django

I am trying to add a Prefix(YNT) to the primary key in django model

Models.py

class testmodel(models.Model):
    product_id = models.IntegerField(max_length=500, primary_key=True)
    product_short_code = models.CharField(max_length=500, default=0, null=True)

How Can I do That ? also instead of starting the primary key from 1 can I start it from 1000 ?

I want the table to look like this

product_id    product_short_code

YNT1000        PP001
YNT1001        PL023

Upvotes: 0

Views: 1972

Answers (4)

xpy
xpy

Reputation: 5621

I think you should see the primary key as a internal Django mechanism to reference and link objects.

Then if you want another, human readable id you can always create a char field product_id that would be as simple as 'YNT' + str(1000+id) which you can save using the post_save signal. You can also add an index to said field to make querying faster if needed.

Example:

@receiver(post_save, sender=Product)
def set_product_id(instance, created, **_kwargs):
    if created:
        instance.product_id = 'YNT' + str(1000 + instance.id)

But still, your relations should be on the default pk and not on the id.

Upvotes: 0

Nalin Dobhal
Nalin Dobhal

Reputation: 2342

There are some approaches that you should follow to achieve this:

1. If Prefix is common for all the entries then you can create a field in your model and add the prefix while getting the value.

class testmodel(models.Model):
    product_code = models.IntegerField(db_index=True)
    product_short_code = models.CharField(max_length=500, default=0, null=True)

    @property
    def product_id(self):
        return f"YNT{self.product_code}"

2. If Prefix is not common for all the entries then you can create a field in your model to store the prefix and add the prefix while getting the value.

class testmodel(models.Model):
    product_code = models.IntegerField(db_index=True)
    product_prefix = models.CharField(max_length=20, default='YNT')
    product_short_code = models.CharField(max_length=500, default=0, null=True)

    @property
    def product_id(self):
        return f"{self.product_prefix}{self.product_code}"

3. If you want to create CharField as primary_key then you 

def create_id():
    // code for creating unique ids. assuming the id will be stored in _id variable.
    return f"YNT{_id}"

class testmodel(models.Model):
    product_id = models.CharField(primary_key=True, max_length=20, default=create_id)
    product_short_code = models.CharField(max_length=500, default=0, null=True)

With the 3rd approach you have to make sure the primary key is always unique.

Upvotes: 0

Adem Öztaş
Adem Öztaş

Reputation: 21446

I think, It is not a good idea using string as a primary key. You can use helper method like on the following.

class testmodel(models.Model):
    product_short_code = models.CharField(max_length=500, default=0, null=True)

    def product_id(self):
       return f'YNT{self.id}'

Upvotes: 1

Vaibhav Mishra
Vaibhav Mishra

Reputation: 227

Please change IntegerField to CharField in testmodel class.

class testmodel(models.Model):
    product_id = models.CharField(max_length=500, primary_key=True)
    product_short_code = models.CharField(max_length=500, default=0, null=True)

If you want that your primary key start any given specific number. Please follow above link. How can my Model primary key start with a specific number?

Upvotes: 0

Related Questions