196 lines
6.9 KiB
Python
196 lines
6.9 KiB
Python
import copy
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from django.db.models.query import QuerySet, EmptyQuerySet, insert_query
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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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def ensure_default_manager(sender, **kwargs):
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"""
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Ensures that a Model subclass contains a default manager and sets the
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_default_manager attribute on the class. Also sets up the _base_manager
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points to a plain Manager instance (which could be the same as
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_default_manager if it's not a subclass of Manager).
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"""
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cls = sender
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if cls._meta.abstract:
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return
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if not getattr(cls, '_default_manager', None):
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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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cls._base_manager = cls.objects
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elif not getattr(cls, '_base_manager', None):
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default_mgr = cls._default_manager.__class__
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if (default_mgr is Manager or
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getattr(default_mgr, "use_for_related_fields", False)):
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cls._base_manager = cls._default_manager
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else:
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# Default manager isn't a plain Manager class, or a suitable
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# replacement, so we walk up the base class hierarchy until we hit
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# something appropriate.
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for base_class in default_mgr.mro()[1:]:
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if (base_class is Manager or
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getattr(base_class, "use_for_related_fields", False)):
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cls.add_to_class('_base_manager', base_class())
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return
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raise AssertionError("Should never get here. Please report a bug, including your model and model manager setup.")
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signals.class_prepared.connect(ensure_default_manager)
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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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self._set_creation_counter()
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self.model = None
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self._inherited = False
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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 getattr(model, '_default_manager', None) or self.creation_counter < model._default_manager.creation_counter:
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model._default_manager = self
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if model._meta.abstract or self._inherited:
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model._meta.abstract_managers.append((self.creation_counter, name,
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self))
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else:
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model._meta.concrete_managers.append((self.creation_counter, name,
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self))
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def _set_creation_counter(self):
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"""
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Sets the creation counter value for this instance and increments the
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class-level copy.
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"""
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self.creation_counter = Manager.creation_counter
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Manager.creation_counter += 1
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def _copy_to_model(self, model):
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"""
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Makes a copy of the manager and assigns it to 'model', which should be
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a child of the existing model (used when inheriting a manager from an
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abstract base class).
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"""
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assert issubclass(model, self.model)
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mgr = copy.copy(self)
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mgr._set_creation_counter()
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mgr.model = model
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mgr._inherited = True
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return mgr
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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 customize the behavior 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 aggregate(self, *args, **kwargs):
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return self.get_query_set().aggregate(*args, **kwargs)
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def annotate(self, *args, **kwargs):
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return self.get_query_set().annotate(*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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def values_list(self, *args, **kwargs):
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return self.get_query_set().values_list(*args, **kwargs)
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def update(self, *args, **kwargs):
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return self.get_query_set().update(*args, **kwargs)
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def reverse(self, *args, **kwargs):
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return self.get_query_set().reverse(*args, **kwargs)
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def defer(self, *args, **kwargs):
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return self.get_query_set().defer(*args, **kwargs)
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def only(self, *args, **kwargs):
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return self.get_query_set().only(*args, **kwargs)
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def _insert(self, values, **kwargs):
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return insert_query(self.model, values, **kwargs)
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def _update(self, values, **kwargs):
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return self.get_query_set()._update(values, **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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class EmptyManager(Manager):
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def get_query_set(self):
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return self.get_empty_query_set()
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