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from collections import defaultdict
from django.apps import apps
from django.db import models
from django.db.models import Q
from django.utils.translation import gettext_lazy as _
class ContentTypeManager(models.Manager):
use_in_migrations = True
def __init__(self, *args, **kwargs):
super().__init__(*args, **kwargs)
# Cache shared by all the get_for_* methods to speed up
# ContentType retrieval.
self._cache = {}
def get_by_natural_key(self, app_label, model):
try:
ct = self._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
return model._meta
def _get_from_cache(self, opts):
key = (opts.app_label, opts.model_name)
return self._cache[self.db][key]
def get_for_model(self, model, for_concrete_model=True):
"""
Return 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:
# 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
# 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,
)
self._add_to_cache(self.db, ct)
return ct
def get_for_models(self, *models, for_concrete_models=True):
"""
Given *models, return a dictionary mapping {model: content_type}.
"""
results = {}
# Models that aren't already in the cache grouped by app labels.
needed_models = defaultdict(set)
# Mapping of opts to the list of models requiring it.
needed_opts = defaultdict(list)
for model in models:
opts = self._get_opts(model, for_concrete_models)
try:
ct = self._get_from_cache(opts)
except KeyError:
needed_models[opts.app_label].add(opts.model_name)
needed_opts[(opts.app_label, opts.model_name)].append(model)
else:
results[model] = ct
if needed_opts:
# Lookup required content types from the DB.
condition = Q(
*(
Q(("app_label", app_label), ("model__in", models))
for app_label, models in needed_models.items()
),
_connector=Q.OR,
)
cts = self.filter(condition)
for ct in cts:
opts_models = needed_opts.pop((ct.app_label, ct.model), [])
for model in opts_models:
results[model] = ct
self._add_to_cache(self.db, ct)
# Create content types that weren't in the cache or DB.
for (app_label, model_name), opts_models in needed_opts.items():
ct = self.create(app_label=app_label, model=model_name)
self._add_to_cache(self.db, ct)
for model in opts_models:
results[model] = ct
return results
def get_for_id(self, id):
"""
Lookup a ContentType by ID. Use the same shared cache as get_for_model
(though ContentTypes are not created on-the-fly by get_by_id).
"""
try:
ct = self._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.
"""
self._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._cache.setdefault(using, {})[key] = ct
self._cache.setdefault(using, {})[ct.id] = ct
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.app_labeled_name
@property
def name(self):
model = self.model_class()
if not model:
return self.model
return str(model._meta.verbose_name)
@property
def app_labeled_name(self):
model = self.model_class()
if not model:
return self.model
return "%s | %s" % (
model._meta.app_config.verbose_name,
model._meta.verbose_name,
)
def model_class(self):
"""Return the 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, using=None, **kwargs):
"""
Return 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(using).get(**kwargs)
def get_all_objects_for_this_type(self, **kwargs):
"""
Return all objects of this type for the keyword arguments given.
"""
return self.model_class()._base_manager.filter(**kwargs)
def natural_key(self):
return (self.app_label, self.model)
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