#22571: Document implications of using auto_now_add=True and get_or_create
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Reporter: nu.everest@… | Owner: nobody
Type: | Status: new
Cleanup/optimization | Version: 1.4
Component: Documentation | Resolution:
Severity: Normal | Triage Stage: Accepted
Keywords: integrityerror | Needs documentation: 0
auto_now_add get_or_create | Patch needs improvement: 0
duplicatekey | UI/UX: 0
Has patch: 0 |
Needs tests: 0 |
Easy pickings: 0 |
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Comment (by charettes):
Replying to [comment:4 mardini]:
> Note that your date_added is a DateTimeField, not a DateField, so it
takes time into account. That's why using "today's date" won't match the
existing value of date_added (since it's today's date + a particular
time). If however some_datetime_obj in your first is exactly the same date
and time, no new object will be created. If you don't want to consider the
time in your get_or_create(), you can either use a DateField for
date_added, or filter against year/month/day of your DateTimeField. So I
think this ticket is invalid.
I agree that the second example is a bit wrong but there's a legitimate
issue to be documented here.
{{{#!python
from django.db import models
from django.utils import timezone
class Auto(models.Model):
added = models.DateTimeField(auto_now_add=True)
class Default(models.Model):
added = models.DateTimeField(default=timezone.now)
}}}
{{{#!python
In [1]: from app.models import Auto, Default, timezone
In [2]: added = timezone.now()
In [3]: Auto.objects.get_or_create(added=added)
Out[3]: (<Auto: Auto object>, True)
In [4]: Auto.objects.get_or_create(added=added)
Out[4]: (<Auto: Auto object>, True)
In [5]: Default.objects.get_or_create(added=added)
Out[5]: (<Default: Default object>, True)
In [6]: Default.objects.get_or_create(added=added)
Out[6]: (<Default: Default object>, False)
}}}
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Ticket URL: <https://code.djangoproject.com/ticket/22571#comment:5>
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