def generic_aggregate(qs_model, generic_qs_model, aggregator, gfk_field=None):
"""
Find total number of comments on blog entries:
generic_aggregate(Entry.objects.public(), Comment.objects.public(), Count('comments__id'))
Find the average rating for foods starting with 'a':
a_foods = Food.objects.filter(name__startswith='a')
generic_aggregate(a_foods, Rating, Avg('ratings__rating'))
.. note::
In both of the above examples it is assumed that a GenericRelation exists
on Entry to Comment (named "comments") and also on Food to Rating (named "ratings").
If a GenericRelation does *not* exist, the query will still return correct
results but the code path will be different as it will use the fallback method.
.. warning::
If the underlying column type differs between the qs_model's primary
key and the generic_qs_model's foreign key column, it will use the fallback
method, which can correctly CASTself.
:param qs_model: A model or a queryset of objects you want to perform
annotation on, e.g. blog entries
:param generic_qs_model: A model or queryset containing a GFK, e.g. comments
:param aggregator: an aggregation, from django.db.models, e.g. Count('id') or Avg('rating')
:param gfk_field: explicitly specify the field w/the gfk
"""
prepared_query = prepare_query(qs_model, generic_qs_model, aggregator, gfk_field)
if prepared_query is not False:
return prepared_query.aggregate(aggregate=aggregator)["aggregate"]
else:
# need to fall back since CAST will be missing
return fallback_generic_aggregate(qs_model, generic_qs_model, aggregator, gfk_field)
def generic_aggregate(qs_model, generic_qs_model, aggregator, gfk_field=None):
"""
Find total number of comments on blog entries:
generic_aggregate(Entry.objects.public(), Comment.objects.public(), Count('comments__id'))
Find the average rating for foods starting with 'a':
a_foods = Food.objects.filter(name__startswith='a')
generic_aggregate(a_foods, Rating, Avg('ratings__rating'))
.. note::
In both of the above examples it is assumed that a GenericRelation exists
on Entry to Comment (named "comments") and also on Food to Rating (named "ratings").
If a GenericRelation does *not* exist, the query will still return correct
results but the code path will be different as it will use the fallback method.
.. warning::
If the underlying column type differs between the qs_model's primary
key and the generic_qs_model's foreign key column, it will use the fallback
method, which can correctly CASTself.
:param qs_model: A model or a queryset of objects you want to perform
annotation on, e.g. blog entries
:param generic_qs_model: A model or queryset containing a GFK, e.g. comments
:param aggregator: an aggregation, from django.db.models, e.g. Count('id') or Avg('rating')
:param gfk_field: explicitly specify the field w/the gfk
"""
prepared_query = prepare_query(qs_model, generic_qs_model, aggregator,
gfk_field)
if prepared_query is not False:
return prepared_query.aggregate(aggregate=aggregator)['aggregate']
else:
# need to fall back since CAST will be missing
return fallback_generic_aggregate(qs_model, generic_qs_model,
aggregator, gfk_field)
def generic_aggregate(self, *args, **kwargs):
return fallback_generic_aggregate(*args, **kwargs)
def generic_aggregate(self, *args, **kwargs):
return fallback_generic_aggregate(*args, **kwargs)
