Generating unique random field in Django or PostgreSQL

Question

I have this model

class Inscription(models.Model):
    person = models.ForeignKey(Person)
    congress = models.ForeignKey(Congress)
    folio = models.IntegerField(max_length=4, editable=False)

I need the folio attribute to be unique within the same congress, but repeatable in the table, but it's important that generated random numbers are not repeated (instead of validating if it already exists and then generate a new one).

Is there any way to achieve this? It doesnt matter if the work is to be done in Django or PostgreSQL

Thank you for reading.

Sandeep Hukku · Accepted Answer · 2017-01-18 18:54:28Z

2

if you can change the type of folio field to CharField, then you can use uuid.

import uuid
x = str(uuid.uuid1())

The x will always be unique and you will never need to check the value for duplicate in the Model. Hope this helps.

answered Jan 18, 2017 at 18:54

Sandeep Hukku

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5 Comments

Jorge Solis Over a year ago

Thank you, but the folio must be a number between 0 and 1000, even if it's a CharField, also it must be unique for the congress it's related to, not in the whole table. Example: There's the congress1 and I have 50 people attending to it, with their random folios, lets say person8 has folio number 472 Then, the next congress (congress2) may have a person1 with folio nomber 472

Sandeep Hukku Over a year ago

if that is the case move the folio field to congress.

Jorge Solis Over a year ago

the folio is a number that identifies each participant (not all the people stored paticipate in every congress, and previous participant may partipate again)

Sandeep Hukku Over a year ago

In that case you can use random module to generate a random integer import random r = random.Random() random_int=r.randint(0,1000). This will give you random integer. After that filter with the generated random int and see if there is any entry with the same congress object. If there is then try again with the above code else save.

Jorge Solis Over a year ago

Yes, actually that's the way it works now (in the database), but I was looking for a method that prevent the already existing numbers from being generated again (so that no validation will be necessary)

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