285 lines
10 KiB
Python
285 lines
10 KiB
Python
import copy
|
|
import inspect
|
|
from importlib import import_module
|
|
|
|
from django.db import router
|
|
from django.db.models.query import QuerySet
|
|
from django.utils import six
|
|
from django.utils.encoding import python_2_unicode_compatible
|
|
|
|
|
|
def ensure_default_manager(cls):
|
|
"""
|
|
Ensures that a Model subclass contains a default manager and sets the
|
|
_default_manager attribute on the class. Also sets up the _base_manager
|
|
points to a plain Manager instance (which could be the same as
|
|
_default_manager if it's not a subclass of Manager).
|
|
"""
|
|
if cls._meta.swapped:
|
|
setattr(cls, 'objects', SwappedManagerDescriptor(cls))
|
|
return
|
|
if not getattr(cls, '_default_manager', None):
|
|
if any(f.name == 'objects' for f in cls._meta.fields):
|
|
raise ValueError(
|
|
"Model %s must specify a custom Manager, because it has a "
|
|
"field named 'objects'" % cls.__name__
|
|
)
|
|
# Create the default manager, if needed.
|
|
cls.add_to_class('objects', Manager())
|
|
cls._base_manager = cls.objects
|
|
elif not getattr(cls, '_base_manager', None):
|
|
default_mgr = cls._default_manager.__class__
|
|
if (default_mgr is Manager or
|
|
getattr(default_mgr, "use_for_related_fields", False)):
|
|
cls._base_manager = cls._default_manager
|
|
else:
|
|
# Default manager isn't a plain Manager class, or a suitable
|
|
# replacement, so we walk up the base class hierarchy until we hit
|
|
# something appropriate.
|
|
for base_class in default_mgr.mro()[1:]:
|
|
if (base_class is Manager or
|
|
getattr(base_class, "use_for_related_fields", False)):
|
|
cls.add_to_class('_base_manager', base_class())
|
|
return
|
|
raise AssertionError(
|
|
"Should never get here. Please report a bug, including your "
|
|
"model and model manager setup."
|
|
)
|
|
|
|
|
|
@python_2_unicode_compatible
|
|
class BaseManager(object):
|
|
# Tracks each time a Manager instance is created. Used to retain order.
|
|
creation_counter = 0
|
|
|
|
#: If set to True the manager will be serialized into migrations and will
|
|
#: thus be available in e.g. RunPython operations
|
|
use_in_migrations = False
|
|
|
|
def __new__(cls, *args, **kwargs):
|
|
# We capture the arguments to make returning them trivial
|
|
obj = super(BaseManager, cls).__new__(cls)
|
|
obj._constructor_args = (args, kwargs)
|
|
return obj
|
|
|
|
def __init__(self):
|
|
super(BaseManager, self).__init__()
|
|
self._set_creation_counter()
|
|
self.model = None
|
|
self.name = None
|
|
self._inherited = False
|
|
self._db = None
|
|
self._hints = {}
|
|
|
|
def __str__(self):
|
|
""" Return "app_label.model_label.manager_name". """
|
|
return '%s.%s' % (self.model._meta.label, self.name)
|
|
|
|
def deconstruct(self):
|
|
"""
|
|
Returns a 5-tuple of the form (as_manager (True), manager_class,
|
|
queryset_class, args, kwargs).
|
|
|
|
Raises a ValueError if the manager is dynamically generated.
|
|
"""
|
|
qs_class = self._queryset_class
|
|
if getattr(self, '_built_with_as_manager', False):
|
|
# using MyQuerySet.as_manager()
|
|
return (
|
|
True, # as_manager
|
|
None, # manager_class
|
|
'%s.%s' % (qs_class.__module__, qs_class.__name__), # qs_class
|
|
None, # args
|
|
None, # kwargs
|
|
)
|
|
else:
|
|
module_name = self.__module__
|
|
name = self.__class__.__name__
|
|
# Make sure it's actually there and not an inner class
|
|
module = import_module(module_name)
|
|
if not hasattr(module, name):
|
|
raise ValueError(
|
|
"Could not find manager %s in %s.\n"
|
|
"Please note that you need to inherit from managers you "
|
|
"dynamically generated with 'from_queryset()'."
|
|
% (name, module_name)
|
|
)
|
|
return (
|
|
False, # as_manager
|
|
'%s.%s' % (module_name, name), # manager_class
|
|
None, # qs_class
|
|
self._constructor_args[0], # args
|
|
self._constructor_args[1], # kwargs
|
|
)
|
|
|
|
def check(self, **kwargs):
|
|
return []
|
|
|
|
@classmethod
|
|
def _get_queryset_methods(cls, queryset_class):
|
|
def create_method(name, method):
|
|
def manager_method(self, *args, **kwargs):
|
|
return getattr(self.get_queryset(), name)(*args, **kwargs)
|
|
manager_method.__name__ = method.__name__
|
|
manager_method.__doc__ = method.__doc__
|
|
return manager_method
|
|
|
|
new_methods = {}
|
|
# Refs http://bugs.python.org/issue1785.
|
|
predicate = inspect.isfunction if six.PY3 else inspect.ismethod
|
|
for name, method in inspect.getmembers(queryset_class, predicate=predicate):
|
|
# Only copy missing methods.
|
|
if hasattr(cls, name):
|
|
continue
|
|
# Only copy public methods or methods with the attribute `queryset_only=False`.
|
|
queryset_only = getattr(method, 'queryset_only', None)
|
|
if queryset_only or (queryset_only is None and name.startswith('_')):
|
|
continue
|
|
# Copy the method onto the manager.
|
|
new_methods[name] = create_method(name, method)
|
|
return new_methods
|
|
|
|
@classmethod
|
|
def from_queryset(cls, queryset_class, class_name=None):
|
|
if class_name is None:
|
|
class_name = '%sFrom%s' % (cls.__name__, queryset_class.__name__)
|
|
class_dict = {
|
|
'_queryset_class': queryset_class,
|
|
}
|
|
class_dict.update(cls._get_queryset_methods(queryset_class))
|
|
return type(class_name, (cls,), class_dict)
|
|
|
|
def contribute_to_class(self, model, name):
|
|
# TODO: Use weakref because of possible memory leak / circular reference.
|
|
self.model = model
|
|
if not self.name:
|
|
self.name = name
|
|
# Only contribute the manager if the model is concrete
|
|
if model._meta.abstract:
|
|
setattr(model, name, AbstractManagerDescriptor(model))
|
|
elif model._meta.swapped:
|
|
setattr(model, name, SwappedManagerDescriptor(model))
|
|
else:
|
|
# if not model._meta.abstract and not model._meta.swapped:
|
|
setattr(model, name, ManagerDescriptor(self))
|
|
if (not getattr(model, '_default_manager', None) or
|
|
self.creation_counter < model._default_manager.creation_counter):
|
|
model._default_manager = self
|
|
|
|
abstract = False
|
|
if model._meta.abstract or (self._inherited and not self.model._meta.proxy):
|
|
abstract = True
|
|
model._meta.managers.append((self.creation_counter, self, abstract))
|
|
|
|
def _set_creation_counter(self):
|
|
"""
|
|
Sets the creation counter value for this instance and increments the
|
|
class-level copy.
|
|
"""
|
|
self.creation_counter = BaseManager.creation_counter
|
|
BaseManager.creation_counter += 1
|
|
|
|
def _copy_to_model(self, model):
|
|
"""
|
|
Makes a copy of the manager and assigns it to 'model', which should be
|
|
a child of the existing model (used when inheriting a manager from an
|
|
abstract base class).
|
|
"""
|
|
assert issubclass(model, self.model)
|
|
mgr = copy.copy(self)
|
|
mgr._set_creation_counter()
|
|
mgr.model = model
|
|
mgr._inherited = True
|
|
return mgr
|
|
|
|
def db_manager(self, using=None, hints=None):
|
|
obj = copy.copy(self)
|
|
obj._db = using or self._db
|
|
obj._hints = hints or self._hints
|
|
return obj
|
|
|
|
@property
|
|
def db(self):
|
|
return self._db or router.db_for_read(self.model, **self._hints)
|
|
|
|
#######################
|
|
# PROXIES TO QUERYSET #
|
|
#######################
|
|
|
|
def get_queryset(self):
|
|
"""
|
|
Returns a new QuerySet object. Subclasses can override this method to
|
|
easily customize the behavior of the Manager.
|
|
"""
|
|
return self._queryset_class(self.model, using=self._db, hints=self._hints)
|
|
|
|
def all(self):
|
|
# We can't proxy this method through the `QuerySet` like we do for the
|
|
# rest of the `QuerySet` methods. This is because `QuerySet.all()`
|
|
# works by creating a "copy" of the current queryset and in making said
|
|
# copy, all the cached `prefetch_related` lookups are lost. See the
|
|
# implementation of `RelatedManager.get_queryset()` for a better
|
|
# understanding of how this comes into play.
|
|
return self.get_queryset()
|
|
|
|
def __eq__(self, other):
|
|
return (
|
|
isinstance(other, self.__class__) and
|
|
self._constructor_args == other._constructor_args
|
|
)
|
|
|
|
def __ne__(self, other):
|
|
return not (self == other)
|
|
|
|
def __hash__(self):
|
|
return id(self)
|
|
|
|
|
|
class Manager(BaseManager.from_queryset(QuerySet)):
|
|
pass
|
|
|
|
|
|
class ManagerDescriptor(object):
|
|
# This class ensures managers aren't accessible via model instances.
|
|
# For example, Poll.objects works, but poll_obj.objects raises AttributeError.
|
|
def __init__(self, manager):
|
|
self.manager = manager
|
|
|
|
def __get__(self, instance, type=None):
|
|
if instance is not None:
|
|
raise AttributeError("Manager isn't accessible via %s instances" % type.__name__)
|
|
return self.manager
|
|
|
|
|
|
class AbstractManagerDescriptor(object):
|
|
# This class provides a better error message when you try to access a
|
|
# manager on an abstract model.
|
|
def __init__(self, model):
|
|
self.model = model
|
|
|
|
def __get__(self, instance, type=None):
|
|
raise AttributeError("Manager isn't available; %s is abstract" % (
|
|
self.model._meta.object_name,
|
|
))
|
|
|
|
|
|
class SwappedManagerDescriptor(object):
|
|
# This class provides a better error message when you try to access a
|
|
# manager on a swapped model.
|
|
def __init__(self, model):
|
|
self.model = model
|
|
|
|
def __get__(self, instance, type=None):
|
|
raise AttributeError("Manager isn't available; %s has been swapped for '%s'" % (
|
|
self.model._meta.object_name, self.model._meta.swapped
|
|
))
|
|
|
|
|
|
class EmptyManager(Manager):
|
|
def __init__(self, model):
|
|
super(EmptyManager, self).__init__()
|
|
self.model = model
|
|
|
|
def get_queryset(self):
|
|
return super(EmptyManager, self).get_queryset().none()
|