118 lines
4.0 KiB
Python
118 lines
4.0 KiB
Python
from django.db.models.query import QuerySet, EmptyQuerySet
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from django.dispatch import dispatcher
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from django.db.models import signals
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from django.db.models.fields import FieldDoesNotExist
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# Size of each "chunk" for get_iterator calls.
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# Larger values are slightly faster at the expense of more storage space.
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GET_ITERATOR_CHUNK_SIZE = 100
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def ensure_default_manager(sender):
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cls = sender
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if not hasattr(cls, '_default_manager'):
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# Create the default manager, if needed.
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try:
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cls._meta.get_field('objects')
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raise ValueError, "Model %s must specify a custom Manager, because it has a field named 'objects'" % cls.__name__
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except FieldDoesNotExist:
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pass
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cls.add_to_class('objects', Manager())
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dispatcher.connect(ensure_default_manager, signal=signals.class_prepared)
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class Manager(object):
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# Tracks each time a Manager instance is created. Used to retain order.
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creation_counter = 0
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def __init__(self):
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super(Manager, self).__init__()
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# Increase the creation counter, and save our local copy.
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self.creation_counter = Manager.creation_counter
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Manager.creation_counter += 1
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self.model = None
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def contribute_to_class(self, model, name):
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# TODO: Use weakref because of possible memory leak / circular reference.
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self.model = model
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setattr(model, name, ManagerDescriptor(self))
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if not hasattr(model, '_default_manager') or self.creation_counter < model._default_manager.creation_counter:
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model._default_manager = self
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#######################
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# PROXIES TO QUERYSET #
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#######################
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def get_empty_query_set(self):
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return EmptyQuerySet(self.model)
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def get_query_set(self):
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"""Returns a new QuerySet object. Subclasses can override this method
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to easily customise the behaviour of the Manager.
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"""
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return QuerySet(self.model)
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def none(self):
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return self.get_empty_query_set()
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def all(self):
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return self.get_query_set()
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def count(self):
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return self.get_query_set().count()
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def dates(self, *args, **kwargs):
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return self.get_query_set().dates(*args, **kwargs)
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def distinct(self, *args, **kwargs):
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return self.get_query_set().distinct(*args, **kwargs)
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def extra(self, *args, **kwargs):
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return self.get_query_set().extra(*args, **kwargs)
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def get(self, *args, **kwargs):
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return self.get_query_set().get(*args, **kwargs)
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def get_or_create(self, **kwargs):
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return self.get_query_set().get_or_create(**kwargs)
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def create(self, **kwargs):
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return self.get_query_set().create(**kwargs)
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def filter(self, *args, **kwargs):
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return self.get_query_set().filter(*args, **kwargs)
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def complex_filter(self, *args, **kwargs):
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return self.get_query_set().complex_filter(*args, **kwargs)
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def exclude(self, *args, **kwargs):
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return self.get_query_set().exclude(*args, **kwargs)
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def in_bulk(self, *args, **kwargs):
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return self.get_query_set().in_bulk(*args, **kwargs)
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def iterator(self, *args, **kwargs):
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return self.get_query_set().iterator(*args, **kwargs)
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def latest(self, *args, **kwargs):
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return self.get_query_set().latest(*args, **kwargs)
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def order_by(self, *args, **kwargs):
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return self.get_query_set().order_by(*args, **kwargs)
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def select_related(self, *args, **kwargs):
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return self.get_query_set().select_related(*args, **kwargs)
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def values(self, *args, **kwargs):
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return self.get_query_set().values(*args, **kwargs)
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class ManagerDescriptor(object):
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# This class ensures managers aren't accessible via model instances.
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# For example, Poll.objects works, but poll_obj.objects raises AttributeError.
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def __init__(self, manager):
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self.manager = manager
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def __get__(self, instance, type=None):
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if instance != None:
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raise AttributeError, "Manager isn't accessible via %s instances" % type.__name__
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return self.manager
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