#36030: Rendering decimal to SQL is incoherent and leads to bugs. It relays on
str
formating not type.
-------------------------------------+-------------------------------------
Reporter: Bartłomiej Nowak | Owner: (none)
Type: Bug | Status: closed
Component: Database layer | Version: 5.1
(models, ORM) |
Severity: Normal | Resolution: needsinfo
Keywords: | Triage Stage:
| Unreviewed
Has patch: 0 | Needs documentation: 0
Needs tests: 0 | Patch needs improvement: 0
Easy pickings: 0 | UI/UX: 0
-------------------------------------+-------------------------------------
Comment (by Bartłomiej Nowak):
I am using Postgres.
{{{
SomeModel.objects.create(some_field_of_type_int=2)
sm = SomeModel.objects.annotate(x=F("some_field_of_type_int") /
Decimal(3.0)).get()
sm.x # returns 0
}}}
It will render Decimal of 3.0 to the query as 3 (INT). Because str(...)
from Decimal(3.0) returns 3. (See cases at description)
At python is not a problem, but at database it is, cus it breaks types.
Calculation of two INTs at postgres, will return int as well, which is in
this case 0, instead of 0.6666, which database would produce, if Django
would render 3.0 instead of 3.
Therefore, Django will return Decimal('0'), which I consider as Bug. This
is not what anyone suppose to get.
--
Ticket URL: <https://code.djangoproject.com/ticket/36030#comment:3>
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