The aim of this proposal is to reuse Q objects for models that are related
through FK or M2M fields.
A simplified example would be a Q object like
>>> is_blue = Q(blue=True)
>>> Thing.objects.filter(is_blue)
that should be reused to filter the owners of things:
>>> User.objects.filter(things__blue=True).
Currently, the only way to reuse the Q object would be subquery:
>>> User.objects.filter(things__in=Thing.objects.filter(is_blue)).
I therefore propose the following API:
>>> Q(lookup=value).push('relfield')
which would be equivalent to
>>> Q(relfield__lookup=value)
and
>>> qs.filter(relfield=Q(lookup=value))
which would be equivalent to
>>> qs.filter(Q(lookup=value).push('relfield')).
We then could write
>>> User.objects.filter(things=is_blue)
which is shorter and produces more natural SQL than the subquery solution.
Thoughs? Suggestions?
__
Johannes
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