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query.py
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query.py
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from __future__ import unicode_literals
from itertools import chain
import django
from django.db.models.query import EmptyQuerySet, QuerySet
class CompositeQuerySet(object):
"""
A queryset like object composed of multiple querysets
"""
def __init__(self, querysets):
self._querysets = tuple(querysets)
self.model = self.querysets[0].model
assert all(qs.model == self.model for qs in self.querysets[1:]), \
'All querysets must be of the same model'
@property
def querysets(self):
return self._querysets
def __iter__(self):
return chain(*self.querysets)
def get(self, *args, **kwargs):
for qs in self.querysets:
try:
obj = qs.get(*args, **kwargs)
except self.model.DoesNotExist:
pass
else:
return obj
raise self.model.DoesNotExist
def _compose(self, method, *args, **kwargs):
return self.__class__(getattr(qs, method)(*args, **kwargs)
for qs in self.querysets)
def filter(self, *args, **kwargs):
return self._compose('filter', *args, **kwargs)
def distinct(self):
return self._compose('distinct')
def exists(self):
return any(qs.exists() for qs in self.querysets)
class EmptyDynamicChoicesQuerySet(EmptyQuerySet):
def filter_for_instance(self):
return self
class DynamicChoicesQuerySet(QuerySet):
def _clone(self, *args, **kwargs):
clone = super(DynamicChoicesQuerySet, self)._clone(*args, **kwargs)
clone._field = self._field
return clone
if django.VERSION >= (1, 6):
def filter_for_instance(self, instance, data):
if self.query.is_empty():
return self
return self._field._invoke_choices_callback(instance, self, data)
else:
def filter_for_instance(self, instance, data):
return self._field._invoke_choices_callback(instance, self, data)
def none(self):
return self._clone(klass=EmptyDynamicChoicesQuerySet)
def dynamic_queryset_factory(queryset, field):
clone = queryset._clone(DynamicChoicesQuerySet)
clone._field = field
return clone