id	summary	reporter	owner	description	type	status	component	version	severity	resolution	keywords	cc	stage	has_patch	needs_docs	needs_tests	needs_better_patch	easy	ui_ux
27791	update_or_create() doesn't work properly when model has auto_now=True	Andrew Chiw	nobody	"I'm writing an exchange rate app:

models.py
{{{
from django.db import models


class ExchangeRate(models.Model):
    base = models.CharField(max_length=3)
    target = models.CharField(max_length=3)
    rate = models.DecimalField(max_digits=17, decimal_places=8)
    date = models.DateField(auto_now=True)

    def __str__(self):
        return ""{}->{} on {}"".format(self.base, self.target, str(self.date))

    class Meta:
        unique_together = ((""base"", ""target"", ""date""),)

}}}

fx.py
{{{
from datetime import datetime, date
import requests

from .models import ExchangeRate


def get_eur_rates():
    url = 'http://api.fixer.io/latest'
    eur_rates = requests.get(url).json()
    print(eur_rates)
    for target in eur_rates[""rates""]:
        import ipdb; ipdb.set_trace()
        ExchangeRate.objects.update_or_create(base=""EUR"", target=target, date=eur_rates[""date""], defaults={""rate"": eur_rates[""rates""][target]})
    print(ExchangeRate.objects.all())
}}}

I already have ExchangeRate objects in the database from 2017-01-29.
Now, when I want to run update_or_create() with date='2017-01-27', it fails:

{{{
ipdb> ExchangeRate.objects.update_or_create(base=""EUR"", target=target, date='2017-01-27', defaults={""rate"": eur_rates[""
rates""][target]})
*** django.db.utils.IntegrityError: duplicate key value violates unique constraint ""fx_exchangerate_base_f6916782_uniq""
DETAIL:  Key (base, target, date)=(EUR, CZK, 2017-01-29) already exists.
}}}

I'm sure Django is working internally in a way that might result in this error, but this shouldn't happen and the error message is confusing."	Bug	closed	Database layer (models, ORM)	1.10	Normal	invalid			Unreviewed	0	0	0	0	0	0