I see much value in aggregating on a single page (rather than the entire
QS).
Check out this
example:
https://cloud.githubusercontent.com/assets/1499307/18555738/964622e0-7b71-11e6-9a53-3a525ba25b4b.png
Also, my current implementation (in the pull request) does support a
user-friendly name for the field, like so:
class EmployeeAdmin(admin.ModelAdmin):
list_display = ('name', 'age', 'formatted_monthly_salary')
list_aggregates = (('age', Avg), ('formatted_monthly_salary', Sum))
def formatted_monthly_salary(self, employee_or_salary):
salary = getattr(employee_or_salary, 'monthly_salary',
employee_or_salary)
return '${0:,.2f}'.format(salary)
formatted_monthly_salary.admin_aggregate_field = 'monthly_salary'
On Thursday, September 22, 2016 at 8:52:20 PM UTC+3, Andrew Mosson wrote:
>
> We have an implementation of both annotations in *list_display* and
> adding an aggregates for the entire list (which we call *list_summary*
> and what you are calling here *list_aggregates*) and there are a bunch of
> subtleties in the interaction due to Admin's built in support for
> pagination and filtering
>
> To demonstrate, let's use a simplified use case
> assume models such as Author -< Book >- Genre (Book has FKs to both
> Author and Genre)
>
> and and admin such as (as suggested in Stack Overflow post that Tim
> referenced (​already possible to some extent
> <http://stackoverflow.com/questions/22517999/django-admin-interface-to-display-aggregates>
> )
>
> class AuthorAdmin(admin.ModelAdmin):
> list_display = ('author_name', 'book_count', 'book_sum_price')
> list_filters = ('book__genre__name', )
> list_summary = (('Total Books', Sum('book_count'), ),
> ('Total Book Price', Sum('book_sum_price'), ))
>
> def get_queryset(self, request):
> return super(BookAdmin, self).get_queryset(request).annotate(
> books_count=Count('books__name'),
> books_sum_price=Sum('books__price'))
>
> With regards to *list_summary* (or *list_aggregates* in the PR) our
> implementation summarizes the entire QuerySet not just a single page (my
> quick read of the patch seems to indicate that list_aggregates only
> aggregates a single page of the qs). From my perspective summarizing a
> single page doesn't provide as much value summarizing the entire QS. If
> one agrees with that then feature will would have to support a user
> friendly name for the field (implemented here as a tuple - as suggested by
> Jim). Additionally, if the feature summarizes the entire qs then the
> output should likely go above the table rather than as summary below (if it
> were below and the results were paginated, it would likely confuse the
> users)
>
> With regards to extending list_display to support annotations there are
> subtle interactions between admin, annotated query sets and filters.
>
> The qs that Django executes when the user has a filter looks like
>
> Author.objects.annotate(...).filter(...)
>
> In the code shown above this will produce the correct result set, but
> because annotate and filter aren't commutative
> <https://docs.djangoproject.com/en/1.10/topics/db/aggregation/#order-of-annotate-and-filter-clauses>,
>
> the generated SQL ends up joining the Books table twice. Additionally,
> there are probably some cases where complex filters will give unexpected
> results.
>
> Give that the user really wants
>
> Author.objects.filter(...).annotate(...)
>
> we ended up adding a modelAdmin.get_annotations(...) method and
> subclassing ChangeList to implement this feature.
>
> One additional note is that annotations require implementing a method on
> the modelAdmin class for each annotations which seems very boilerplate-ish.
> We have extended *list_display* to automatically handle the boilerplate
> as well.
>
> Since we use this extensively these features in our applications, we would
> be excited to see them implemented as part of admin. We'd be happy to
> contribute here and if this seems like its worth pursuing I'll ask our team
> to look into refactoring the work we've done so that it could live in core
> rather than as sub-classes.
>
> On Wednesday, September 21, 2016 at 6:17:27 PM UTC-7, Josh Smeaton wrote:
>>
>> I think I'm OK with `list_aggregates` because it implies a terminal
>> queryset method which really restricts the members used to create that
>> aggregation (the GROUP BY). Adding aggregates to existing list_display
>> would require something *else* to refine the group by using `values()`.
>>
>> If list_aggregates is a useful feature, then this sounds like an
>> appropriate way to implement that. Regular annotations could be added and
>> processed within list_display, provided list_display was modified to accept
>> expressions (either aggregates or regular annotations) in tuple form for
>> alias support.
>>
>> list_aggregates -> queryset.aggregate()
>> list_display -> queryset.annotate(annotations).values()
>>
>> Does that make sense?
>>
>
--
You received this message because you are subscribed to the Google Groups
"Django developers (Contributions to Django itself)" group.
To unsubscribe from this group and stop receiving emails from it, send an email
to django-developers+unsubscr...@googlegroups.com.
To post to this group, send email to django-developers@googlegroups.com.
Visit this group at https://groups.google.com/group/django-developers.
To view this discussion on the web visit
https://groups.google.com/d/msgid/django-developers/01f63ba0-b1f3-4148-8b74-ceed782cafb7%40googlegroups.com.
For more options, visit https://groups.google.com/d/optout.
