#25177: Filter reference field on model to a date difference raise a TypeError
-------------------------------------+-------------------------------------
Reporter: Mounir | Owner: nobody
Type: Bug | Status: new
Component: Database layer | Version: 1.8
(models, ORM) |
Severity: Normal | Resolution:
Keywords: | Triage Stage: Accepted
Has patch: 0 | Needs documentation: 0
Needs tests: 0 | Patch needs improvement: 0
Easy pickings: 0 | UI/UX: 0
-------------------------------------+-------------------------------------
Comment (by Mariusz Felisiak):
Replying to [comment:2 Josh Smeaton]:
> This ticket seems really familiar, but I can't seem to find a duplicate
at the moment. I'll keep hunting for it. In the mean time, there's a
workaround for what you want to do:
>
> {{{
>
Product.objects.annotate(days=ExpressionWrapper(F('start_date')-F('signed_date'),
output_field=DurationField())).filter(days__lte=2)
> }}}
>
> That works on Postgres at least, I'm not sure how other backends handle
it.
>
> I think `Combinable._combine()` may need special handling for `date -
date` producing durations though.
This issue is not about combined expressions and LHS of a lookup, it's
about RHS. Django calls `get_db_prep_lookup()` on LHS values when it's
defined for the LHS output field. Currently the following example raises
`AttributeError` on SQLite and MySQL, and `ProgrammingError` on PostgreSQL
and Oracle (where `DurationField.get_db_prep_lookup()` is no-op).
{{{
Experiment.objects.annotate(days=F('start')-F('end')).filter(days__lte=11)
}}}
- SQLite and MySQL:
{{{
File "/home/felixx/repo/django/django/utils/duration.py", line 46, in
duration_microseconds
return (24 * 60 * 60 * delta.days + delta.seconds) * 1000000 +
delta.microseconds
^^^^^^^^^^
AttributeError: 'int' object has no attribute 'days'
}}}
- Oracle and PostgreSQL:
{{{
django.db.utils.ProgrammingError: operator does not exist: interval <=
integer
LINE 1: ...art" - "expressions_ExPeRiMeNt"."end"))::interval <= 11 ORDE...
}}}
but it works fine when RHS is `timedelta` on all databases:
{{{
Experiment.objects.annotate(days=F('start')-F('end')).filter(days__lte=datetime.timedelta(11))
}}}
I'm not sure if there is anything to fix here.
--
Ticket URL: <https://code.djangoproject.com/ticket/25177#comment:3>
Django <https://code.djangoproject.com/>
The Web framework for perfectionists with deadlines.
--
You received this message because you are subscribed to the Google Groups
"Django updates" group.
To unsubscribe from this group and stop receiving emails from it, send an email
to [email protected].
To view this discussion visit
https://groups.google.com/d/msgid/django-updates/0107019a746c8d1f-4625b702-9584-44f5-a128-7180846c7a65-000000%40eu-central-1.amazonses.com.
