How do I configure Tastypie to treat a field as unique?

Question

How do I configure Tastypie to treat a field as unique? My expectation would be to receive some sort of non-500 error (possibly a 409 conflict?) as a response if I try to insert duplicate entries for the field marked as unique.

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I've looked through the docs and it looks like it should be obvious to me, but for some reason I'm not getting the response I would expect to see.

Here's the documentation link:

http://readthedocs.org/docs/django-tastypie/en/latest/fields.html?highlight=unique

---

The sample code is as follows:

urls.py

v1_api = Api(api_name='v1')
v1_api.register(CompanyResource())

urlpatterns = patterns('',
    (r'^api/', include(v1_api.urls)),
)

resource.py

class CompanyResource(ModelResource):

    CompanyName = fields.CharField(attribute='company_name')
    CompanyId = fields.CharField(attribute='company_id', unique=True)
    Contact = fields.CharField(attribute='contact')
    Email = fields.CharField(attribute='email')
    Phone = fields.CharField(attribute='phone')

    class Meta:
        queryset = Company.objects.all()
        authentication = BasicAuthentication()
        authorization = Authorization()
        allowed_methods = ['get', 'post']

models.py

class Company(models.Model):

    company_name = models.TextField(default=None, blank=True, null=True)
    company_id = models.CharField(default='', unique=True, db_index=True, max_length=20)
    contact = models.TextField(default=None, blank=True, null=True)
    email = models.EmailField(default=None, blank=True, null=True)
    phone = models.TextField(default=None, blank=True, null=True)

---

The error I receive is the following (using curl to hit my local service):

curl --dump-header - -H "Content-Type: application/json" -X POST --user user:password --data '{"CompanyName": "company", "CompanyId": "1234567890", "Contact": "John", "Email": "[email protected]", "Phone": "555-555-5555"}' http://localhost:8000/api/v1/company/
HTTP/1.0 500 INTERNAL SERVER ERROR
Date: Thu, 15 Sep 2011 18:25:20 GMT
Server: WSGIServer/0.1 Python/2.7.1
Content-Type: application/json; charset=utf-8

{"error_message": "(1062, \"Duplicate entry '1234567890' for key 'api_company_company_id_uniq'\")", 
...<snip>...
raise errorclass, errorvalue\n\nIntegrityError: (1062, \"Duplicate entry '1234567890' for key 'api_company_company_id_uniq'\")\n"}

When I remove unique=True, db_index=True, from the Company model, I don't receive the Integrity error, but instead, a new, duplicate resource is created. Again, this isn't the expected result as I would expect unique to preform some validation and cause some non-500 response.

Rabe

The answer for me was to use validation=FormValidation(form_class=<MyModelForm>). This validates against your model's fields. – Kabyle

Answer 1

Here is how I solved the problem:

Based on the documentation for validation, I was able to implement a custom validator that checked the uniqueness of the field for me. http://django-tastypie.readthedocs.org/en/latest/validation.html

In the CompanyResource, I added to the class meta a CustomValidation. I placed the implementation for CustomValidation in a validations.py file. If isValid returns errors, the api will return a 400 with the messages included in errors.

class CompanyResource(ModelResource):
    """
    CompanyIds should be unique
    """     
    CompanyName = fields.CharField(attribute='company_name')     
    CompanyId = fields.CharField(attribute='company_id', unique=True)     
    Contact = fields.CharField(attribute='contact')     
    Email = fields.CharField(attribute='email')     
    Phone = fields.CharField(attribute='phone')    

    class Meta:        
        queryset = Company.objects.all()        
        authentication = BasicAuthentication()        
        authorization = Authorization()        
        allowed_methods = ['get', 'post']                
        validation = CustomValidation()

validations.py

class CustomValidation(Validation):
    """
    The custom validation checks two things:
       1) that there is data
       2) that the CompanyId exists (unique check)
    """
    def is_valid(self, bundle, request=None):
        if not bundle.data:
            return {'__all__': 'Missing data, please include CompanyName, CompanyId, Contact, Email, and Phone.'}

        errors = {}                                    
        company_id=bundle.data.get('CompanyId', None)

        # manager method, returns true if the company exists, false otherwise
        if Company.objects.company_exists(company_id):
            errors['CompanyId']='Duplicate CompanyId, CompanyId %s already exists.' % company_id
        return errors

Rabe

It doesn't. If you need PUT support you would need to go 'thoslins' approach above. – Moriahmoriarty

Answer 2

I had the same problem today. Here is how I deal with it:

Override [request_method]_[request_type] method in your resource definition. For example, I override post_list in FooResource:

def post_list(self, request, **kwargs):
    from django.db import IntegrityError
    try:
        return super(FooResource, self).post_list(request, **kwargs)
    except IntegrityError, e:
        if e.args[0] == 1062:
            return http.HttpConflict()

Hope it works for you.

Narvaez

Why did you choose to import IntegrityError inside the method? – Hurry

Answer 3

For what it's worth, I've created a slightly different solution that works better for me. It's based on thoslin's answer.

I found that the e.args[0] == 1062 check fails for me. I'm pretty sure this is a MySQL error and I'm using Postgres.

I also implemented this in the obj_create method so that it will handle all object creation, not just that done via post_list.

from tastypie.exceptions import ImmediateHttpResponse
from tastypie.http import HttpConflict
from django.db import IntegrityError

...

class MyBaseResource(ModelResource):
    def obj_create(self, bundle, **kwargs):
        try:
            return super(MyBaseResource, self).obj_create(bundle, **kwargs)
        except IntegrityError, e:
            if e.args[0] == 1062 or e.args[0].startswith('duplicate key'):
                raise ImmediateHttpResponse(HttpConflict())

...

class MyResource(MyBaseResource):
    [usual resource stuff]

Hurry