Here is my problem. I am trying to load some data that has a natural key relationship to another model.
I modified the parent model to generate natural keys.
I exported the the data from the old database using the command:
manage.py dumpdata resources.image -n --indent 4 > images.json
I then tried to import into the new database using the command:
manage.py loaddata images.json
At this point I get the error:
IntegrityError: Problem installing fixtures: The row in table 'resources_image'
with primary key '340' has an invalid foreign key: resources_image.voyage_id contains
a value '41890' that does not have a corresponding value in voyage_voyage.id.
It is trying to query on voyage_voyage.id instead of voyage_voyage.voyage_id as specified in the get_by_natural_key function. I double checked and the key in the fixture is in the voyage_id field. Below is my code and sample fixture.
Parent Model:
# for parsing natural key
class VoyageManager(models.Manager):
def get_by_natural_key(self, voyage_id):
return self.get(voyage_id=voyage_id)
class Voyage(models.Model):
# for parsing natural key
objects = VoyageManager()
voyage_id = models.IntegerField("Voyage ID (can be empty)", null=True, blank=True)
# A WHOLE BUNCH OF FIELDS
# generate natural key
def natural_key(self):
return (self.voyage_id)
class Meta:
ordering = ['voyage_id',]
verbose_name = 'Voyage'
verbose_name_plural = "Voyages"
def __unicode__(self):
return "Voyage #%s" % str(self.voyage_id)
Child Model:
class Image(models.Model):
voyage = models.ForeignKey(Voyage, null=True, blank=True)
# MANY OTHER FIELDS
class Meta:
verbose_name = "Image"
verbose_name_plural = "Images"
ordering = ["date"]
The Fixture:
{
"pk": 340,
"model": "resources.image",
"fields": {
"category": 56,
"voyage": 41890,
"date": 1873,
"description": "blah blah blah",
"language": " ",
"creator": null,
"title": "Catherine Zimmermann-Mulgrave, \nc.1873",
"source": "blah blah blah",
"ready_to_go": true,
"file": "images/5AF81DA065049ACE0EC8E236C445F5BC.JPG",
"order_num": 0
}
}
So here is what I finally figured out
This function expects the input to come from a tuple:
def get_by_natural_key(self, voyage_id):
return self.get(voyage_id=voyage_id)
This function produces the tuple when --natural flag is specified
def natural_key(self):
return (self.voyage_id)
The trick here is that when you have a tuple with only one element it reverts back to its original type (str, int etc.) to force a single element tuple you need a trailing "," so the fix is :
def natural_key(self):
return (self.voyage_id,)
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