Unique field problem

[vale hawk]

I have a Profile model where I have this unique field

referral_code = models.CharField(max_length=200, unique=True)

I have a generate_ref_code() that generate a code.
How can I make sure that this code is unique for the field?

new_ref_code = generate_ref_code()
Profile.objects.create(user=instance, referral_code=new_ref_code)

I can't do like

try:
   new_ref_code = generate_ref_code()
   Profile.objects.create(user=instance, referral_code=new_ref_code)
except IntegityError:
    # generate a new code and try again

Because
IntegrityError exception only occur when try to save it

Profile.objects.create(user=instance, referral_code=new_ref_code).save() 

Therefore how can I check this uniqueness of the code.

[crude rose]

You would need to show us generate_ref_code() before we can help

[vale hawk]

def generate_ref_code():
   alpha_num = string.ascii_letters + string.digits
   new_code = ''.join(secrets.choice(alpha_num) for i in range(6))
   return new_code

[crude rose]

why not just use python's build in uuid or secrets?

def generate_ref_code():
return uuid.uuid4```

that's what I generally use for my referral / invite codes, and I have yet to have it duplicate one

[vale hawk]

Can I limit the length to 6?

[crude rose]

that I don't know, I know you can with secrets

but, if you're having issues with uniquity, longer would be better for you

also, copyright Thalimet 2023, Uniquity

lol

[vale hawk]

How can I make it unique? I wanna check it in the database of it already exist then try to generate new one and that is also exists then try again

[crude rose]

that's an expensive, and flawed way of doing it

the more codes that are generated, the longer that is likely to take

[vale hawk]

How can I go about doing it the best practices way

[crude rose]

one sec

[vale hawk]

I can't make it longer because it's a requirement.

[crude rose]

lol, tell the marketing people to leave the technical decisions to the people implementing them 😛

(kidding, mostly)

def generate_ref_code():
  return secrets.token_hex(3)```

give that a try

you can check that against the database if you want, but using the token hex function of secrets should generate a pretty unique code

[vale hawk]

How can I check it against the data base

[crude rose]

I'd say you already have the logic built in

if there's an integrity error on that field, generate a new one and try again

[vale hawk]

What's the better way to check against the database

[crude rose]

16,777,216 - btw this is the max possible combinations that can exist for a six character string like that

[vale hawk]

That occurs when try to save but. I need a way to check it before saving

[crude rose]

ok, so, do you know how to filter?

you could take the generated code, filter for objects that have that code as the relevant attribute

if any exist in the queryset, then you can generate another code

[vale hawk]

Wait I can do something with objects.get() because it returns only one unique objects. If there is two objects then it raise exception, so if return object then not unique, if Doesn'tExist exception then the code is unique otherwise if the exception is different then multiple exists

[crude rose]

it's easier with filter

[vale hawk]

Can I do something like that?

[crude rose]

because you can do objects.filter(attribute=blah).exists()

and it returns a true/false value

[vale hawk]

Mmm . exists better then checking multiple exceptions

[crude rose]

multiples can't exist under your schema

so it wouldn't matter 😄

[vale hawk]

Thanks I will implement this

[crude rose]

cheers 🙂

[vale hawk]

secrets.token_urlsafe

[crude rose]

hex (should) be url safe, I think?

[vale hawk]

what does urlsafe mean here I didn't find any explanation in doc

[crude rose]

it probably means it won't generate characters that can't be used in a url

like , or /

but that's educated guess, not direct knowledge 🙂

[vale hawk]

There's hex too. But seen this urlsafe so got curious

[crude rose]

so hex would generate characters that are either 0-9 or a-f

so, all of those would defacto be url safe

[vale hawk]

Oo that's a good idea so the code can be use easily in url routing

[crude rose]

yeah

[vale hawk]

I got it now

[crude rose]

hex should do that automatically

but it looks like urlsafe() adds in extra characters that hex doesn't

ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789-_

[vale hawk]

Oo

Thanks again

[crude rose]

so yeah urlsafe would probably be a better choice for you

better chances at being unique

[vale hawk]

Okay