#26010: I need to count objects in a queryset by year and month
-------------------------------------+-------------------------------------
Reporter: mahmoodkhan | Owner: nobody
Type: New feature | Status: closed
Component: Database layer | Version: master
(models, ORM) |
Severity: Normal | Resolution: invalid
Keywords: Queryset.extra | Triage Stage:
| Unreviewed
Has patch: 0 | Needs documentation: 0
Needs tests: 0 | Patch needs improvement: 0
Easy pickings: 0 | UI/UX: 0
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Comment (by mahmoodkhan):
Thanks! much appreciated.
Replying to [comment:1 charettes]:
> Hi mahmoodkhan,
>
> You don't `extra()` to achieve this. There's already a couple of open
tickets that you can relate to (#25774 comes to mind) but you should
annotate your queryset with a
[https://docs.djangoproject.com/en/1.9/ref/models/lookups/#transform-
reference Transform] in order to extract the year and months.
>
> If you don't want to write your own Transform subclass you can use the
undocumented `MonthTransform` and `YearTransform` to annotate your
queryset:
>
> {{{#!python
> from django.db.models.lookups import MonthTransform as Month,
YearTransform as Year
>
> Item.objects.annotate(
> year=Year('date'),
> month=Month('date'),
> ).values('year', 'month').annotate(count=Count('pk'))
> }}}
>
> Keep in mind that you're relying on a private API (used internally to
implement the `__month` and `__year` lookups) that might be moved around
or replaced.
>
> Once `values()` allows transforms and lookups you should be able to
simply do this:
>
> {{{#!python
> Item.objects.values('date__year',
'date__month').annotate(count=Count('pk'))
> }}}
--
Ticket URL: <https://code.djangoproject.com/ticket/26010#comment:2>
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