loaddata not looking for natural keys

[bobhaugen]

loaddata error message:

File "/home/bob/.virtualenvs/vn2/lib/python2.6/site-packages/django/core/serializers/json.py", line 47, in Deserializer

    raise DeserializationError(e)

DeserializationError: [u"'Cash Contribution' value must be an integer."]

Here's how I dumped the data:

./manage.py dumpdata valueaccounting.AgentType  valueaccounting.Facet valueaccounting.FacetValue valueaccounting.ProcessPattern valueaccounting.PatternFacetValue  valueaccounting.Project --natural --indent=4 > starters.json

Then I did syncdb and migrate.

Then I tried loaddata:

./manage.py loaddata starters.json

Here's the offending json:

    {

        "pk": 22, 

        "model": "valueaccounting.patternfacetvalue", 

        "fields": {

            "facet_value": 4, 

            "pattern": 9, 

            "event_type": "Cash Contribution"

        }

    }, 

Here's the relevant natural key code:

class EventTypeManager(models.Manager):

    def get_by_natural_key(self, name):

        return self.get(name=name)

class EventType(models.Model):

[...]

    objects = EventTypeManager()

    def natural_key(self):

        return (self.name)

So what am I missing?  (I put a pdb trace in the get_by_natural_key method, never got called.) 

I am stumped. But I expect it is some stupid mistake that I can't see...

[bobhaugen]

Oh, and I am using Django 1.4.5.

[bobhaugen]

Ok, now I am really confused.

Here's the code where the error originates in django/core/serializers/python.py:

           # Handle FK fields

            elif field.rel and isinstance(field.rel, models.ManyToOneRel):

                if field_value is not None:

                    import pdb; pdb.set_trace()

                    if hasattr(field.rel.to._default_manager, 'get_by_natural_key'):

                        if hasattr(field_value, '__iter__'):

                            obj = field.rel.to._default_manager.db_manager(db).get_by_natural_key(*field_value)

                            value = getattr(obj, field.rel.field_name)

                            # If this is a natural foreign key to an object that

                            # has a FK/O2O as the foreign key, use the FK value

                            if field.rel.to._meta.pk.rel:

                                value = value.pk

                        else:

                            value = field.rel.to._meta.get_field(field.rel.field_name).to_python(field_value)

                        data[field.attname] = value

                    else:

                        data[field.attname] = field.rel.to._meta.get_field(field.rel.field_name).to_python(field_value)

                else:

                    data[field.attname] = None

Here's what pdb says:

(Pdb) p field

<django.db.models.fields.related.ForeignKey: event_type>

(Pdb) p field_value

u'Cash Contribution'

(Pdb) p hasattr(field.rel.to._default_manager, 'get_by_natural_key')

True

(Pdb) n

> /home/bob/.virtualenvs/vn2/lib/python2.6/site-packages/django/core/serializers/python.py(109)Deserializer()

-> if hasattr(field_value, '__iter__'):

(Pdb) p hasattr(field_value, '__iter__')

False

(Pdb) p field_value

u'Cash Contribution'

(Pdb) p type(field_value)

<type 'unicode'>

(Pdb) n

> /home/bob/.virtualenvs/vn2/lib/python2.6/site-packages/django/core/serializers/python.py(117)Deserializer()

-> value = field.rel.to._meta.get_field(field.rel.field_name).to_python(field_value)

(Pdb) n

ValidationError: Validati...teger."])

> /home/bob/.virtualenvs/vn2/lib/python2.6/site-packages/django/core/serializers/python.py(117)Deserializer()

-> value = field.rel.to._meta.get_field(field.rel.field_name).to_python(field_value)

I thought unicode fields had iterators? But here's one in ipython:

In [15]: field_value = u'Cash Contribution'

In [16]: field_value.__iter__()

---------------------------------------------------------------------------

AttributeError                            Traceback (most recent call last)

/home/bob/.virtualenvs/vn2/valuenetwork/<ipython console> in <module>()

AttributeError: 'unicode' object has no attribute '__iter__'

[bobhaugen]

Got a clue. I re-read the doc and it says the natural  key value must be a tuple.  Missed that before.

So I changed it like this:

    def natural_key(self):

        return (self.name,)

In the shell, that properly returns a tuple:

(u'Cash Contribution',)

But in the dumpdata results, it is not a tuple:

    {

        "pk": 22, 

        "model": "valueaccounting.patternfacetvalue", 

        "fields": {

            "facet_value": 4, 

            "pattern": 9, 

            "event_type": [

                "Cash Contribution"

            ]

        }

    }, 

So I am still missing something.

[bobhaugen]

Not a tuple, it's now a json array. (Still not seeing things accurately...)

So I would think it would deserialize with __iter__, but I still get the same deserialization error message.

[bobhaugen]

Ok, problem resolved.

I must have done something else wrong the last time I did loaddata, because I tried the whole sequence again with the natural_keys as tuples, and it all worked.

Sorry to bother the list so much.

But to summarize, natural_keys must be tuples, not single unicode values.