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from __future__ import unicode_literals
from django.apps import apps
from django.db import models
from django.db.utils import IntegrityError, OperationalError, ProgrammingError
from django.utils.encoding import force_text, python_2_unicode_compatible
from django.utils.translation import ugettext_lazy as _
class ContentTypeManager(models.Manager):
use_in_migrations = True
# Cache to avoid re-looking up ContentType objects all over the place.
# This cache is shared by all the get_for_* methods.
_cache = {}
def get_by_natural_key(self, app_label, model):
try:
ct = self.__class__._cache[self.db][(app_label, model)]
except KeyError:
ct = self.get(app_label=app_label, model=model)
self._add_to_cache(self.db, ct)
return ct
def _get_opts(self, model, for_concrete_model):
if for_concrete_model:
model = model._meta.concrete_model
elif model._deferred:
model = model._meta.proxy_for_model
return model._meta
def _get_from_cache(self, opts):
key = (opts.app_label, opts.model_name)
return self.__class__._cache[self.db][key]
def get_for_model(self, model, for_concrete_model=True):
"""
Returns the ContentType object for a given model, creating the
ContentType if necessary. Lookups are cached so that subsequent lookups
for the same model don't hit the database.
"""
opts = self._get_opts(model, for_concrete_model)
try:
return self._get_from_cache(opts)
except KeyError:
pass
# The ContentType entry was not found in the cache, therefore we
# proceed to load or create it.
try:
try:
# We start with get() and not get_or_create() in order to use
# the db_for_read (see #20401).
ct = self.get(app_label=opts.app_label, model=opts.model_name)
except self.model.DoesNotExist:
# Not found in the database; we proceed to create it. This time we
# use get_or_create to take care of any race conditions.
ct, created = self.get_or_create(
app_label=opts.app_label,
model=opts.model_name,
)
except (OperationalError, ProgrammingError, IntegrityError):
# It's possible to migrate a single app before contenttypes,
# as it's not a required initial dependency (it's contrib!)
# Have a nice error for this.
raise RuntimeError(
"Error creating new content types. Please make sure contenttypes "
"is migrated before trying to migrate apps individually."
)
self._add_to_cache(self.db, ct)
return ct
def get_for_models(self, *models, **kwargs):
"""
Given *models, returns a dictionary mapping {model: content_type}.
"""
for_concrete_models = kwargs.pop('for_concrete_models', True)
# Final results
results = {}
# models that aren't already in the cache
needed_app_labels = set()
needed_models = set()
needed_opts = set()
for model in models:
opts = self._get_opts(model, for_concrete_models)
try:
ct = self._get_from_cache(opts)
except KeyError:
needed_app_labels.add(opts.app_label)
needed_models.add(opts.model_name)
needed_opts.add(opts)
else:
results[model] = ct
if needed_opts:
cts = self.filter(
app_label__in=needed_app_labels,
model__in=needed_models
)
for ct in cts:
model = ct.model_class()
if model._meta in needed_opts:
results[model] = ct
needed_opts.remove(model._meta)
self._add_to_cache(self.db, ct)
for opts in needed_opts:
# These weren't in the cache, or the DB, create them.
ct = self.create(
app_label=opts.app_label,
model=opts.model_name,
)
self._add_to_cache(self.db, ct)
results[ct.model_class()] = ct
return results
def get_for_id(self, id):
"""
Lookup a ContentType by ID. Uses the same shared cache as get_for_model
(though ContentTypes are obviously not created on-the-fly by get_by_id).
"""
try:
ct = self.__class__._cache[self.db][id]
except KeyError:
# This could raise a DoesNotExist; that's correct behavior and will
# make sure that only correct ctypes get stored in the cache dict.
ct = self.get(pk=id)
self._add_to_cache(self.db, ct)
return ct
def clear_cache(self):
"""
Clear out the content-type cache. This needs to happen during database
flushes to prevent caching of "stale" content type IDs (see
django.contrib.contenttypes.management.update_contenttypes for where
this gets called).
"""
self.__class__._cache.clear()
def _add_to_cache(self, using, ct):
"""Insert a ContentType into the cache."""
# Note it's possible for ContentType objects to be stale; model_class() will return None.
# Hence, there is no reliance on model._meta.app_label here, just using the model fields instead.
key = (ct.app_label, ct.model)
self.__class__._cache.setdefault(using, {})[key] = ct
self.__class__._cache.setdefault(using, {})[ct.id] = ct
@python_2_unicode_compatible
class ContentType(models.Model):
app_label = models.CharField(max_length=100)
model = models.CharField(_('python model class name'), max_length=100)
objects = ContentTypeManager()
class Meta:
verbose_name = _('content type')
verbose_name_plural = _('content types')
db_table = 'django_content_type'
unique_together = (('app_label', 'model'),)
def __str__(self):
return self.name
@property
def name(self):
model = self.model_class()
if not model:
return self.model
return force_text(model._meta.verbose_name)
def model_class(self):
"Returns the Python model class for this type of content."
try:
return apps.get_model(self.app_label, self.model)
except LookupError:
return None
def get_object_for_this_type(self, **kwargs):
"""
Returns an object of this type for the keyword arguments given.
Basically, this is a proxy around this object_type's get_object() model
method. The ObjectNotExist exception, if thrown, will not be caught,
so code that calls this method should catch it.
"""
return self.model_class()._base_manager.using(self._state.db).get(**kwargs)
def get_all_objects_for_this_type(self, **kwargs):
"""
Returns all objects of this type for the keyword arguments given.
"""
return self.model_class()._base_manager.using(self._state.db).filter(**kwargs)
def natural_key(self):
return (self.app_label, self.model)
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