#24485: Support for annotate(end=F('start') + F('duration'),
output_field=DateTimeField)
-------------------------------------+-------------------------------------
Reporter: yoyoma | Owner: nobody
Type: New feature | Status: new
Component: Database layer | Version: master
(models, ORM) |
Severity: Normal | Resolution:
Keywords: durationfield, | Triage Stage:
aggregation, annotation | Unreviewed
Has patch: 0 | Needs documentation: 0
Needs tests: 0 | Patch needs improvement: 0
Easy pickings: 0 | UI/UX: 0
-------------------------------------+-------------------------------------
Comment (by jarshwah):
So this has convinced me even more that we need some kind of wrapper type
to provide a top level output_field attribute to the expression, unless
someone has a nicer idea?
I'd suggest something along the lines of:
{{{
Ticket.objects.annotate(expires=Output(F('active_at')+F('duration'),
output_field=DurationField())
}}}
But I'm not sold on the name (or the look of it to be honest).
In the mean time though, you can capture the output of F()+F() outside the
queryset construction, and modify the output_field directly:
{{{
In [16]: expires = F('active_at')+F('duration')
In [17]: expires.output_field = models.DurationField()
In [18]: qs = Ticket.objects.annotate(expires_at=expires)
In [19]: for q in qs:
....: print(q.expires_at)
....:
2015-03-15 23:53:18.065764+00:00
2015-03-16 02:53:53.953573+00:00
2015-03-15 18:53:56.391507+00:00
2015-03-15 21:53:58.441390+00:00
}}}
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Ticket URL: <https://code.djangoproject.com/ticket/24485#comment:4>
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