#29733: update_or_create - documentation misleading
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Reporter: DavidPratten | Owner: nobody
Type: Cleanup/optimization | Status: new
Component: Documentation | Version: 2.1
Severity: Normal | Keywords:
Triage Stage: Unreviewed | Has patch: 0
Needs documentation: 0 | Needs tests: 0
Patch needs improvement: 0 | Easy pickings: 0
UI/UX: 0 |
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When update_or_create searches the table for a record to update it
searches all fields marked 'unique' or 'primary_key'.
In the case where a record has two candidate keys the update_or_create
function will fail to update either the primary key or the candidate key,
leading to an Integrity Error.
https://docs.djangoproject.com/en/2.1/ref/models/querysets/#update-or-
create
This behavour is not 'wrong'. But it is surprising and a time waster.
{{{
class Coa(models.Model):
def __str__(self):
return f'{self.qbac}'
trantype = models.CharField(max_length=255, db_column=u'TranType',
blank=True)
qbac = models.CharField( unique=True, max_length=255,
db_column=u'QBAc')
guid = models.CharField(max_length=32, primary_key=True)
account_type=models.CharField(max_length=20)
}}}
Containing the following record:
{{{
"ACCNT", "Advantage Saver", "c6f30c15c9dd1e5af9143fd7bed99315", "A"
}}}
The following, otherwise sensible, code fails with an IntegrityError
{{{
obj, created =
Coa.objects.update_or_create(guid='c6f30c15c9dd1e5af9143fd7bed99315',
defaults={'trantype': 'ACCNT', 'qbac': 'A', 'account_type': 'A' },)
}}}
because the search is on both guid AND qbac rather than just on guid as
requested by the single field in the !**kwargs.
Recommend clarification in the docu that it is not possible to search only
on one field if there are multiple unique constraints in the model.
David
--
Ticket URL: <https://code.djangoproject.com/ticket/29733>
Django <https://code.djangoproject.com/>
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