On Apr 26, 12:33 pm, "Russell Keith-Magee" <[EMAIL PROTECTED]>
wrote:
> So - here's a slightly modified proposal. Last time this topic came up
> on django-dev, Justin Fagnani made an interesting suggestion which I
> think will answer your objections, and leaves open some interesting
> possibilities for userspace extension. Rather than the
> column__aggregate=alias syntax:
>
> >>> Student.objects.all().annotate(
> Avg('height'), tallest=Max('height'), avg_friend_age=Avg('friend__age')
> )
> The raw idea - the aggregates themselves are tied up into functions
> (Avg, Max, etc) that are constructed as an object. The argument to the
> aggregate is the query column, using the standard double-underscore
> notation if necessary to cross tables. In QS-RF, this syntax is being
> used for cross-table order_by() clauses, so there is an analog there.
I like this a lot - makes much more sense to me than the other syntax,
and I think I prefer it to my proposed dictionary based syntax as
well.
> If the aggregate function is provided as an anonymous argument (e.g.,
> Avg('height')), then the aggregate is asked to provide an appropriate
> alias - for example, Avg() might use 'avg__%s' % field_name. If the
> aggregate function is provided as a kwarg, the kwarg name is used as
> the alias.
Is it necessary to provide an anonymous argument syntax at all? Seeing
just annotate(Avg('height')) left me confused as to what the alias
would be until I read your further explanation. Is there any harm in
requiring the user of the API to always explicitly specify their alias
using keyword argument syntax? Unless there's a really good reason to
provide default aliases I think requiring explicit aliases would be
perfectly reasonable ("explicit is better than implicit").
Cheers,
Simon
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