Re: Incrementing the slug by avoiding Integrity error in django models save method

On Mon, Aug 12, 2013 at 9:46 AM, shiva krishna <shivakrshn49@gmail.com> wrote:
> I have a model with two fields as below
>
> **models.py**
>
> class Publisher(models.Model):
> name = models.CharField(max_length=200)
> slug = models.SlugField(max_length=150, unique=True)
>
> def save(self, *args, **kwargs):
> if not self.id and not self.slug:
> slug = slugify(self.name)
> try:
> slug_exits = Publisher.objects.get(slug=slug)
> if slug_exits:
> self.slug = slug + '_1'
> except Publisher.DoesNotExist:
> self.slug = slug
> super(Publisher, self).save(*args, **kwargs)
>
> Here i am creating a slug based on the `name` field as we can see above
>
> So when we try to create a publisher with `name already exists`, the `save`
> method of the model will add the `_1` to the end.
>
> And when we again try to create a new record with same `name`, an
> `Integrity` error will be raised as below
>
> >> Publisher.objects.create(name="abc")
> result: slug will be "abc"
> >> Publisher.objects.create(name="abc")
> result: slug will be "abc_1"
> >> Publisher.objects.create(name="abc")
> result:
>
> .................
> .................
> 34 del cursor
> 35 del connection
> ---> 36 raise errorclass, errorvalue
> 37
> 38 re_numeric_part = re.compile(r"^(\d+)")
>
> IntegrityError: (1062, "Duplicate entry 'abc_1' for key 'slug'")
>
> So what i am want is if the title/slug already exists in the database and if
> slug contains number in it(at the end like abc`_1`), we should increment it
> that number
>
> So what all i want is to `increment the number in the slug` as below if the
> title/slug already exists in the database
>
> abc
> abc_1
> abc_2
> abc_3
>
> So can anyone please let me know how to implement the above logic of
> incrementing the slug ?
>
> Thanks in advance......
>

You can do this naively easy enough:

def save(self, *args, **kwargs):
if not self.id and not self.slug:
slug = base_slug = slugify(self.name)
for idx in range(99):
if idx:
slug = '%s_%d' % (base_slug, idx)
try:
Publisher.objects.get(slug=slug)
except Publisher.DoesNotExist:
break
super(Publisher, self).save(*args, **kwargs)

This is naive for a couple of reasons:

a) To get the slug for the nth item with the same name, you need to do
n database queries
b) It fails for large numbers of n

Personally, I don't think slugs should conflict - if they conflict it
is no longer a good slug name for that resource. I can see the benefit
of article-name-slug-page-1 -> article-name-slug-page-5, but if you
are doing things like that you should include the page number in the
pre-slugged string.

Cheers

Tom

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