I have 2 tables, a info table and a lookup table. Connected to a postgres DB
class Lookup(models.Model):
lookup=models.CharField(max_length=50)
class Info(models.Model):
multiChoice = ArrayField(models.IntegerField(blank=True),null=True)
Can I create a referential constraint on the multiChoice field such that each value on the field must be one of the ID's of the Lookup table.
Something like this - http://blog.2ndquadrant.com/postgresql-9-3-development-array-element-foreign-keys/
Unfortunately in Postgres 9.3, you won't be able to add a foreign key constraint on the array field. See this answer for more details.
However, you can perform some level of validation within Django models, for example:
class Info(models.Model):
...
def save(self, *args, **kwargs):
# validate all multiChoice belong in lookup
lookup_id_list = Lookup.objects.filter(id__in=self.multiChoice)\
.values_list('id', flat=True)
assert set(lookup_id_list) == set(self.multiChoice)
super(Info, self).save(*args, **kwargs)
Note that this won't prevent someone from creating/updating Info records in the database directly which violate your "constraint".
If your models are in a many-to-many relationship, the correct solution would be to use a ManyToMany field which can guarantee your constraint will not be violated.
Thanks for the help @Derek Kwok. I did somthing similar on the Resource hydrate method.
def hydrate(self,bundle):
#Get the array values from the request bundle eg: "{1,2,3}"
multiChoiceValues=bundle.data['multiChoice'][1:-1].split(',')
#Get the lookup table values from DB
lookupObjs=Lookup.objects.all()
#Compare them
#todo: Improve loop comparisons
for multiChoice in multiChoiceValues:
found=False
for objs in lookupObjs:
if (multiChoice==''+repr(objs.id)):
found=True
break
if (found==False):
#Raise an error if any of the values passed break the referential constraint
raise IntegrityError
return bundle
