def get_cached(self, **kwargs):
"""Gets the model instance from the cache, or, if the instance is not in
the cache, gets it from the database and puts it in the cache.
"""
cache_settings = get_cache_settings(self.model)
lookups = cache_settings.get("lookups")
keys = kwargs.keys()
single_kwarg_match = len(keys) == 1 and keys[0] in lookups
multi_kwarg_match = len(keys) != 1 and any(
sorted(keys) == sorted(lookup) for lookup in lookups if isinstance(lookup, (list, tuple))
)
if not single_kwarg_match and not multi_kwarg_match:
raise ValueError("Caching not allowed with kwargs %s" % ", ".join(keys))
# Get object from cache or db.
key = generate_base_key(self.model, **kwargs)
obj = cache.get(key)
if obj is not None:
if isinstance(obj, ObjectDoesNotExist):
raise self.model.DoesNotExist(repr(obj))
elif isinstance(obj, MultipleObjectsReturned):
raise self.model.MultipleObjectsReturned(repr(obj))
else:
return obj
try:
obj = self.get(**kwargs)
except (ObjectDoesNotExist, MultipleObjectsReturned), e:
# The model-specific subclasses of these exceptions are not
# pickleable, so we cache the base exception and reconstruct the
# specific exception when fetching from the cache.
obj = e.__class__.__base__(repr(e))
cache.set(key, obj, cache_settings.get("timeout"))
raise
def get_cached(self, **kwargs):
"""Gets the model instance from the cache, or, if the instance is not in
the cache, gets it from the database and puts it in the cache.
"""
cache_settings = get_cache_settings(self.model)
lookups = cache_settings.get("lookups")
keys = kwargs.keys()
single_kwarg_match = len(keys) == 1 and keys[0] in lookups
multi_kwarg_match = len(keys) != 1 and any(
sorted(keys) == sorted(lookup)
for lookup in lookups if isinstance(lookup, (list, tuple)))
if not single_kwarg_match and not multi_kwarg_match:
raise ValueError("Caching not allowed with kwargs %s" %
", ".join(keys))
# Get object from cache or db.
key = generate_base_key(self.model, **kwargs)
obj = cache.get(key)
if obj is not None:
if isinstance(obj, ObjectDoesNotExist):
raise self.model.DoesNotExist(repr(obj))
elif isinstance(obj, MultipleObjectsReturned):
raise self.model.MultipleObjectsReturned(repr(obj))
else:
return obj
try:
obj = self.get(**kwargs)
except (ObjectDoesNotExist, MultipleObjectsReturned), e:
# The model-specific subclasses of these exceptions are not
# pickleable, so we cache the base exception and reconstruct the
# specific exception when fetching from the cache.
obj = e.__class__.__base__(repr(e))
cache.set(key, obj, cache_settings.get("timeout"))
raise
def get_many_cached(self, list_of_kwargs):
"""Gets the model instance from the cache, or, if the instance is not in
the cache, gets it from the database and puts it in the cache.
"""
cache_settings = get_cache_settings(self.model)
lookups = cache_settings.get("lookups")
prefetch = cache_settings.get("prefetch")
related = self._get_select_related_from_attrs(self.model, prefetch)
if related:
base_qs = self.all().select_related(*related)
else:
base_qs = self.all()
cache_keys = dict()
for kwargs in list_of_kwargs:
keys = kwargs.keys()
single_kwarg_match = len(keys) == 1 and keys[0] in lookups
multi_kwarg_match = len(keys) != 1 and any(
sorted(keys) == sorted(lookup) for lookup in lookups if isinstance(lookup, (list, tuple))
)
if not single_kwarg_match and not multi_kwarg_match:
raise ValueError("Caching not allowed with kwargs %s" % ", ".join(keys))
# Get object from cache or db.
key = generate_base_key(self.model, **kwargs)
cache_keys[key] = kwargs
objects = cache.get_many(cache_keys.keys())
pending_cache_update = dict()
cached_objects = list()
for key, kwargs in cache_keys.iteritems():
obj = objects.get(key, None)
if obj is not None:
if isinstance(obj, ObjectDoesNotExist):
raise self.model.DoesNotExist(repr(obj))
elif isinstance(obj, MultipleObjectsReturned):
raise self.model.MultipleObjectsReturned(repr(obj))
else:
cached_objects.append(obj)
continue
try:
obj = base_qs.get(**kwargs)
except (ObjectDoesNotExist, MultipleObjectsReturned), e:
# The model-specific subclasses of these exceptions are not
# pickleable, so we cache the base exception and reconstruct the
# specific exception when fetching from the cache.
obj = e.__class__.__base__(repr(e))
cache.set(key, obj, cache_settings.get("timeout"))
raise
self._prefetch_related(obj, prefetch)
self._tag_object_as_from_cache(obj)
pending_cache_update[key] = obj
cached_objects.append(obj)
def install(cls):
"""Sets up the invalidation paths for the cached models in CACHETREE,
and registers signal handlers for each of them.
"""
cls.INVALIDATION_PATHS = {}
for app_label, model in get_cached_models():
cls.validate_lookups(model)
cache_settings = get_cache_settings(model)
attrs = cache_settings.get("prefetch")
cls._add_invalidation_path(model, [], attrs)
cls.connect_signals()
def install(cls):
"""Sets up the invalidation paths for the cached models in CACHETREE,
and registers signal handlers for each of them.
"""
cls.INVALIDATION_PATHS = {}
for app_label, model in get_cached_models():
cls.validate_lookups(model)
cache_settings = get_cache_settings(model)
attrs = cache_settings.get("prefetch")
cls._add_invalidation_path(model, [], attrs)
cls.connect_signals()
def validate_lookups(cls, model):
"""Validates that the lookups correspond to fields within
model._meta.fields, as invalidation cannot be reliably performed
otherwise.
Limiting lookups to model._meta.fields is more restrictive than
Django, which allows model fields defined on a related model to be
used in lookups (e.g. Author.objects.get(authorprofile=authorprofile),
where AuthorProfile has a foreign key pointing to author). In order to
invalidate the original state of a modified instance, cachetree copies
the instance __dict__ in a post-init signal handler and uses it for
invalidation. This __dict__ only contains the values for fields in
model._meta.fields, not values for reverse fields.
Limiting lookups also prevents using lookup separators
(double-underscore). Invalidation determines the cache key to
invalidate using the values on the invalidated instance, so all
lookups must be exact lookups (the default). E.g., if a key was stored
using username__contains="stanley", it would be difficult or
impossible to reconstruct the key to be invalidated based simply on
having an instance with username="******".
Lookup fields are not required to be unique. Since the only use of the
cache is via get_cached, which calls Manager.get, uniqueness is
guaranteed prior to setting instances in the cache. If another
instance is subsequently assigned the same lookup value as a cached
instance, it will trigger invalidation of the cached instance.
Subequent calls to get_cached will raise MultipleObjectsReturned.
"""
lookups = get_cache_settings(model).get("lookups")
valid_fieldnames = ["pk"
] + [field.name for field in model._meta.fields]
for lookup in lookups:
if not isinstance(lookup, (list, tuple)):
lookup = [lookup]
for kwarg in lookup:
if kwarg not in valid_fieldnames:
raise ImproperlyConfigured(
cls.ERROR_MSG_INVALID_FIELD_LOOKUP %
dict(model=model.__name__,
lookup=kwarg,
fields=', '.join(valid_fieldnames)))
def validate_lookups(cls, model):
"""Validates that the lookups correspond to fields within
model._meta.fields, as invalidation cannot be reliably performed
otherwise.
Limiting lookups to model._meta.fields is more restrictive than
Django, which allows model fields defined on a related model to be
used in lookups (e.g. Author.objects.get(authorprofile=authorprofile),
where AuthorProfile has a foreign key pointing to author). In order to
invalidate the original state of a modified instance, cachetree copies
the instance __dict__ in a post-init signal handler and uses it for
invalidation. This __dict__ only contains the values for fields in
model._meta.fields, not values for reverse fields.
Limiting lookups also prevents using lookup separators
(double-underscore). Invalidation determines the cache key to
invalidate using the values on the invalidated instance, so all
lookups must be exact lookups (the default). E.g., if a key was stored
using username__contains="stanley", it would be difficult or
impossible to reconstruct the key to be invalidated based simply on
having an instance with username="******".
Lookup fields are not required to be unique. Since the only use of the
cache is via get_cached, which calls Manager.get, uniqueness is
guaranteed prior to setting instances in the cache. If another
instance is subsequently assigned the same lookup value as a cached
instance, it will trigger invalidation of the cached instance.
Subequent calls to get_cached will raise MultipleObjectsReturned.
"""
lookups = get_cache_settings(model).get("lookups")
valid_fieldnames = ["pk"] + [field.name for field in model._meta.fields]
for lookup in lookups:
if not isinstance(lookup, (list, tuple)):
lookup = [lookup]
for kwarg in lookup:
if kwarg not in valid_fieldnames:
raise ImproperlyConfigured(
cls.ERROR_MSG_INVALID_FIELD_LOOKUP
% dict(model=model.__name__, lookup=kwarg, fields=", ".join(valid_fieldnames))
)
def invalidate_root_instances(self, *instances):
"""Invalidates all possible versions of the cached ``instances``,
using the ``instances``'s lookups and their current field
values. Each instance in ``instances`` must be a root instance,
that is, an instance of one of the top-level models stored in the
cache, not a related model instance.
"""
self.seen_instances.update(instances)
keys = set()
for instance in instances:
model = instance.__class__
instance_variants = [instance]
if hasattr(instance, "_orig_state"):
orig = model()
orig.__dict__ = instance._orig_state
instance_variants.append(orig)
for instance in instance_variants:
cache_settings = get_cache_settings(instance.__class__)
lookups = cache_settings.get("lookups")
for lookup in lookups:
if not isinstance(lookup, (list, tuple)):
lookup = [lookup]
kwargs = {}
for fieldname in lookup:
if fieldname == "pk":
field = model._meta.pk
else:
field = model._meta.get_field(fieldname)
attname = field.get_attname()
kwargs[fieldname] = getattr(instance, attname)
key = generate_base_key(instance.__class__, **kwargs)
keys.add(key)
cache.delete_many(keys)
def invalidate_root_instances(self, *instances):
"""Invalidates all possible versions of the cached ``instances``,
using the ``instances``'s lookups and their current field
values. Each instance in ``instances`` must be a root instance,
that is, an instance of one of the top-level models stored in the
cache, not a related model instance.
"""
self.seen_instances.update(instances)
keys = set()
for instance in instances:
model = instance.__class__
instance_variants = [instance]
if hasattr(instance, "_orig_state"):
orig = model()
orig.__dict__ = instance._orig_state
instance_variants.append(orig)
for instance in instance_variants:
cache_settings = get_cache_settings(instance.__class__)
lookups = cache_settings.get("lookups")
for lookup in lookups:
if not isinstance(lookup, (list, tuple)):
lookup = [lookup]
kwargs = {}
for fieldname in lookup:
if fieldname == "pk":
field = model._meta.pk
else:
field = model._meta.get_field(fieldname)
attname = field.get_attname()
kwargs[fieldname] = getattr(instance, attname)
key = generate_base_key(instance.__class__, **kwargs)
keys.add(key)
cache.delete_many(keys)
