#11886 closed (fixed)
F() expressions don't retain parentheses into final SQL
Reported by: | russellm | Owned by: | nobody |
---|---|---|---|
Component: | Uncategorized | Version: | 1.1 |
Severity: | Keywords: | ||
Cc: | Triage Stage: | Unreviewed | |
Has patch: | no | Needs documentation: | |
Needs tests: | Patch needs improvement: | ||
Easy pickings: | UI/UX: |
Description
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.
Change History (2)
comment:1 Changed 5 years ago by russellm
- Resolution set to fixed
- Status changed from new to closed
comment:2 Changed 5 years ago by russellm
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(In [11581]) Fixed #11886 -- Corrected handling of F() expressions that use parentheses. Thanks to Brent Hagany for the report.