#11886: F() expressions don't retain parentheses into final SQL
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Reporter: russellm | Owner: nobody
Status: new | Milestone:
Component: Uncategorized | Version: 1.1
Keywords: | Stage: Unreviewed
Has_patch: 0 |
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Reported by Brent Hagany on django-users:
I'm having some trouble getting F() expressions to obey my parentheses
when I don't want the default order of operations. For example, given
the model:
{{{
class MyModel(models.Model):
wins = models.DecimalField(max_digits=1, decimal_places=0)
losses = models.DecimalField(max_digits=1, decimal_places=0)
win_percentage = models.DecimalField(max_digits=4, decimal_places=3,
default=Decimal('0.000'))
}}}
I get the following results when trying to calculate the
win_percentage:
{{{
In [1]: MyModel.objects.create(wins=2, losses=4)
Out[1]: <MyModel: MyModel object>
In [2]: MyModel.objects.all().update(win_percentage=F('wins') / (F
('wins') + F('losses')))
Out[2]: 1
# I expect this to return Decimal("0.333")
In [3]: MyModel.objects.get(pk=1).win_percentage
Out[3]: Decimal("5.000")
}}}
It appears to be ignoring the parentheses around F('wins') + F
('losses'), and so instead of 2 / (2 + 4) = .333, I'm getting 2 / 2 +
4 = 5.
--
Ticket URL: <http://code.djangoproject.com/ticket/11886>
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