#34551: Case-When aggregation over aggregated fields doesn't work since 4.2
-------------------------------------+-------------------------------------
Reporter: Denis | Owner: nobody
Roldán |
Type: Bug | Status: new
Component: Database | Version: 4.2
layer (models, ORM) | Keywords: orm, aggregate,
Severity: Normal | case, when, field error, bug
Triage Stage: | Has patch: 0
Unreviewed |
Needs documentation: 0 | Needs tests: 0
Patch needs improvement: 0 | Easy pickings: 0
UI/UX: 0 |
-------------------------------------+-------------------------------------
This same QuerySet was working on 4.1.X and prior versions and stopped
working on 4.2.X:
{{{
annotated_users = users_qs.annotate(
total_things=Subquery(
OtherModel.objects.filter(user_id=OuterRef("pk")).annotate(
total_objs=F("total")
).values("total_objs")
)
)
annotated_users.aggregate(
sum_total_objs=Sum("total_things"),
avg_conversion_rate=Case(
When(
sum_total_objs=0,
then=0,
),
default=Round(
(Sum("sum_total_confirmed_objs") /
Sum("sum_total_objs")) * 100, 2
),
output_field=FloatField(),
)
)
}}}
As you can see `sum_total_objs` is an aggregated field that is also used
on a second field to calculate the conversion rate. To avoid a zero
division problem, we were using a Case-When clause over that field. It
works well on any 4.1 and prior versions but stopped working since 4.2,
raising a `FieldError` like:
`Cannot resolve keyword 'sum_total_objs' into field`
Thanks for the support!
--
Ticket URL: <https://code.djangoproject.com/ticket/34551>
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 on the web visit
https://groups.google.com/d/msgid/django-updates/01070187ffe6259c-869fd94a-bd34-43ca-8286-726858577fba-000000%40eu-central-1.amazonses.com.
