> So I suppose my question is this - are there any operations that return a
queryset that couldn't be captured in a Q object?
Annotations are a good example of operations that cannot be expressed in a
Q object.
On the ticket I suggested relying on the "sticky filter" feature of the ORM
to implement a combinable filter spec.
Sticky filters allow chained filter() calls to reuse aliases, making
filter(lookup=1).filter(lookup=2) equivalent to filter(lookup=1, lookup=2)
while the queryset is marked a "sticky"
They are only used internally by the ORM but I remember a ticket where
Anssii mentioned we wight want to expose the feature through a more
adequate API.
e.g.
with queryset.reuse_aliases() as qs:
qs = qs.filter(lookup=1).filter(lookup=2)
assert qs == queryset.filter(lookup=1, lookup=2)
This would make it easy to implement a "combinable" filter spec and allow
users to solve the issues that have surfaced recently about how the admin
does search and filtering through multiple joins. For example, one could
override get_search_results() to reuse aliases easily by relying on this
method and implementing the "combinable" filter spec class would only be a
matter of creating a composite filter spec that reuse aliases in queryset()
before delegating to each of its nested filters.
Simon
Le vendredi 7 octobre 2016 05:52:02 UTC-4, Andy Baker a écrit :
>
> Actually - my recollection was faulty. As the queryset method always has
> to return a queryset (dur) I am not sure that I'm actually doing anything
> that couldn't be expressed as a Q object. I'm just doing some funky stuff
> to get my queryset in shape.
>
> So I suppose my question is this - are there any operations that return a
> queryset that couldn't be captured in a Q object?
>
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