from sqlalchemy.util import EMPTY_SET
import weakref
from sqlalchemy import util
from sqlalchemy.orm.attributes import PASSIVE_NO_RESULT,PASSIVE_OFF,\
NEVER_SET, NO_VALUE, manager_of_class, \
ATTR_WAS_SET
from sqlalchemy.orm import attributes,exc
import sys
attributes.state = sys.modules['sqlalchemy.orm.state']
class InstanceState(object):
"""tracks state information at the instance level."""
session_id = None
key = None
runid = None
load_options = EMPTY_SET
load_path = ()
insert_order = None
mutable_dict = None
_strong_obj = None
modified = False
expired = False
def __init__(self, obj, manager):
self.class_ = obj.__class__
self.manager = manager
self.obj = weakref.ref(obj, self._cleanup)
@util.memoized_property
def committed_state(self):
return {}
@util.memoized_property
def parents(self):
return {}
@util.memoized_property
def pending(self):
return {}
@util.memoized_property
def callables(self):
return {}
def detach(self):
if self.session_id:
try:
del self.session_id
except AttributeError:
pass
def dispose(self):
self.detach()
del self.obj
def _cleanup(self, ref):
instance_dict = self._instance_dict()
if instance_dict:
try:
instance_dict.remove(self)
except AssertionError:
pass
# remove possible cycles
self.__dict__.pop('callables', None)
self.dispose()
def obj(self):
return None
@property
def dict(self):
o = self.obj()
if o is not None:
return attributes.instance_dict(o)
else:
return {}
@property
def sort_key(self):
return self.key and self.key[1] or (self.insert_order, )
def initialize_instance(*mixed, **kwargs):
self, instance, args = mixed[0], mixed[1], mixed[2:]
manager = self.manager
for fn in manager.events.on_init:
fn(self, instance, args, kwargs)
# LESSTHANIDEAL:
# adjust for the case where the InstanceState was created before
# mapper compilation, and this actually needs to be a MutableAttrInstanceState
if manager.mutable_attributes and self.__class__ is not MutableAttrInstanceState:
self.__class__ = MutableAttrInstanceState
self.obj = weakref.ref(self.obj(), self._cleanup)
self.mutable_dict = {}
try:
return manager.events.original_init(*mixed[1:], **kwargs)
except:
for fn in manager.events.on_init_failure:
fn(self, instance, args, kwargs)
raise
def get_history(self, key, **kwargs):
return self.manager.get_impl(key).get_history(self, self.dict, **kwargs)
def get_impl(self, key):
return self.manager.get_impl(key)
def get_pending(self, key):
if key not in self.pending:
self.pending[key] = PendingCollection()
return self.pending[key]
def value_as_iterable(self, key, passive=PASSIVE_OFF):
"""return an InstanceState attribute as a list,
regardless of it being a scalar or collection-based
attribute.
returns None if passive is not PASSIVE_OFF and the getter returns
PASSIVE_NO_RESULT.
"""
impl = self.get_impl(key)
dict_ = self.dict
x = impl.get(self, dict_, passive=passive)
if x is PASSIVE_NO_RESULT:
return None
elif hasattr(impl, 'get_collection'):
return impl.get_collection(self, dict_, x, passive=passive)
else:
return [x]
def _run_on_load(self, instance):
self.manager.events.run('on_load', instance)
def __getstate__(self):
d = {'instance':self.obj()}
d.update(
(k, self.__dict__[k]) for k in (
'committed_state', 'pending', 'parents', 'modified', 'expired',
'callables', 'key', 'load_options', 'mutable_dict'
) if k in self.__dict__
)
if self.load_path:
d['load_path'] = interfaces.serialize_path(self.load_path)
return d
def __setstate__(self, state):
self.obj = weakref.ref(state['instance'], self._cleanup)
self.class_ = state['instance'].__class__
self.manager = manager = manager_of_class(self.class_)
if manager is None:
raise orm_exc.UnmappedInstanceError(
state['instance'],
"Cannot deserialize object of type %r - no mapper() has"
" been configured for this class within the current Python process!" %
self.class_)
elif manager.mapper and not manager.mapper.compiled:
manager.mapper.compile()
self.committed_state = state.get('committed_state', {})
self.pending = state.get('pending', {})
self.parents = state.get('parents', {})
self.modified = state.get('modified', False)
self.expired = state.get('expired', False)
self.callables = state.get('callables', {})
if self.modified:
self._strong_obj = state['instance']
self.__dict__.update([
(k, state[k]) for k in (
'key', 'load_options', 'mutable_dict'
) if k in state
])
if 'load_path' in state:
self.load_path = interfaces.deserialize_path(state['load_path'])
def initialize(self, key):
"""Set this attribute to an empty value or collection,
based on the AttributeImpl in use."""
self.manager.get_impl(key).initialize(self, self.dict)
def reset(self, dict_, key):
"""Remove the given attribute and any
callables associated with it."""
dict_.pop(key, None)
self.callables.pop(key, None)
def expire_attribute_pre_commit(self, dict_, key):
"""a fast expire that can be called by column loaders during a load.
The additional bookkeeping is finished up in commit_all().
This method is actually called a lot with joined-table
loading, when the second table isn't present in the result.
"""
dict_.pop(key, None)
self.callables[key] = self
def set_callable(self, dict_, key, callable_):
"""Remove the given attribute and set the given callable
as a loader."""
dict_.pop(key, None)
self.callables[key] = callable_
def expire_attributes(self, dict_, attribute_names, instance_dict=None):
"""Expire all or a group of attributes.
If all attributes are expired, the "expired" flag is set to True.
"""
if attribute_names is None:
attribute_names = self.manager.keys()
self.expired = True
if self.modified:
if not instance_dict:
instance_dict = self._instance_dict()
if instance_dict:
instance_dict._modified.discard(self)
else:
instance_dict._modified.discard(self)
self.modified = False
filter_deferred = True
else:
filter_deferred = False
to_clear = (
self.__dict__.get('pending', None),
self.__dict__.get('committed_state', None),
self.mutable_dict
)
for key in attribute_names:
impl = self.manager[key].impl
if impl.accepts_scalar_loader and \
(not filter_deferred or impl.expire_missing or key in dict_):
self.callables[key] = self
dict_.pop(key, None)
for d in to_clear:
if d is not None:
d.pop(key, None)
def __call__(self, **kw):
"""__call__ allows the InstanceState to act as a deferred
callable for loading expired attributes, which is also
serializable (picklable).
"""
if kw.get('passive') is attributes.PASSIVE_NO_FETCH:
return attributes.PASSIVE_NO_RESULT
toload = self.expired_attributes.\
intersection(self.unmodified)
self.manager.deferred_scalar_loader(self, toload)
# if the loader failed, or this
# instance state didn't have an identity,
# the attributes still might be in the callables
# dict. ensure they are removed.
for k in toload.intersection(self.callables):
del self.callables[k]
return ATTR_WAS_SET
@property
def unmodified(self):
"""Return the set of keys which have no uncommitted changes"""
return set(self.manager).difference(self.committed_state)
@property
def unloaded(self):
"""Return the set of keys which do not have a loaded value.
This includes expired attributes and any other attribute that
was never populated or modified.
"""
return set(self.manager).\
difference(self.committed_state).\
difference(self.dict)
@property
def expired_attributes(self):
"""Return the set of keys which are 'expired' to be loaded by
the manager's deferred scalar loader, assuming no pending
changes.
see also the ``unmodified`` collection which is intersected
against this set when a refresh operation occurs.
"""
return set([k for k, v in self.callables.items() if v is self])
def _instance_dict(self):
return None
def _is_really_none(self):
return self.obj()
def modified_event(self, dict_, attr, should_copy, previous, passive=PASSIVE_OFF):
if attr.key not in self.committed_state:
if previous is NEVER_SET:
if passive:
if attr.key in dict_:
previous = dict_[attr.key]
else:
previous = attr.get(self, dict_)
if should_copy and previous not in (None, NO_VALUE, NEVER_SET):
previous = attr.copy(previous)
self.committed_state[attr.key] = previous
if not self.modified:
instance_dict = self._instance_dict()
if instance_dict:
instance_dict._modified.add(self)
self._strong_obj = self.obj()
self.modified = True
def commit(self, dict_, keys):
"""Commit attributes.
This is used by a partial-attribute load operation to mark committed
those attributes which were refreshed from the database.
Attributes marked as "expired" can potentially remain "expired" after
this step if a value was not populated in state.dict.
"""
class_manager = self.manager
for key in keys:
if key in dict_ and key in class_manager.mutable_attributes:
self.committed_state[key] = self.manager[key].impl.copy(dict_[key])
else:
self.committed_state.pop(key, None)
self.expired = False
for key in set(self.callables).\
intersection(keys).\
intersection(dict_):
del self.callables[key]
def commit_all(self, dict_, instance_dict=None):
"""commit all attributes unconditionally.
This is used after a flush() or a full load/refresh
to remove all pending state from the instance.
- all attributes are marked as "committed"
- the "strong dirty reference" is removed
- the "modified" flag is set to False
- any "expired" markers/callables for attributes loaded are removed.
Attributes marked as "expired" can potentially remain "expired" after this step
if a value was not populated in state.dict.
"""
self.__dict__.pop('committed_state', None)
self.__dict__.pop('pending', None)
if 'callables' in self.__dict__:
callables = self.callables
for key in list(callables):
if key in dict_ and callables[key] is self:
del callables[key]
for key in self.manager.mutable_attributes:
if key in dict_:
self.committed_state[key] = self.manager[key].impl.copy(dict_[key])
if instance_dict and self.modified:
instance_dict._modified.discard(self)
self.modified = self.expired = False
self._strong_obj = None
class MutableAttrInstanceState(InstanceState):
"""InstanceState implementation for objects that reference 'mutable'
attributes.
Has a more involved "cleanup" handler that checks mutable attributes
for changes upon dereference, resurrecting if needed.
"""
@util.memoized_property
def mutable_dict(self):
return {}
def _get_modified(self, dict_=None):
if self.__dict__.get('modified', False):
return True
else:
if dict_ is None:
dict_ = self.dict
for key in self.manager.mutable_attributes:
if self.manager[key].impl.check_mutable_modified(self, dict_):
return True
else:
return False
def _set_modified(self, value):
self.__dict__['modified'] = value
modified = property(_get_modified, _set_modified)
@property
def unmodified(self):
"""a set of keys which have no uncommitted changes"""
dict_ = self.dict
return set([
key for key in self.manager
if (key not in self.committed_state or
(key in self.manager.mutable_attributes and
not self.manager[key].impl.check_mutable_modified(self, dict_)))])
def _is_really_none(self):
"""do a check modified/resurrect.
This would be called in the extremely rare
race condition that the weakref returned None but
the cleanup handler had not yet established the
__resurrect callable as its replacement.
"""
if self.modified:
self.obj = self.__resurrect
return self.obj()
else:
return None
def reset(self, dict_, key):
self.mutable_dict.pop(key, None)
InstanceState.reset(self, dict_, key)
def _cleanup(self, ref):
"""weakref callback.
This method may be called by an asynchronous
gc.
If the state shows pending changes, the weakref
is replaced by the __resurrect callable which will
re-establish an object reference on next access,
else removes this InstanceState from the owning
identity map, if any.
"""
if self._get_modified(self.mutable_dict):
self.obj = self.__resurrect
else:
instance_dict = self._instance_dict()
if instance_dict:
try:
instance_dict.remove(self)
except AssertionError:
pass
self.dispose()
def __resurrect(self):
"""A substitute for the obj() weakref function which resurrects."""
# store strong ref'ed version of the object; will revert
# to weakref when changes are persisted
obj = self.manager.new_instance(state=self)
self.obj = weakref.ref(obj, self._cleanup)
self._strong_obj = obj
obj.__dict__.update(self.mutable_dict)
# re-establishes identity attributes from the key
self.manager.events.run('on_resurrect', self, obj)
# TODO: don't really think we should run this here.
# resurrect is only meant to preserve the minimal state needed to
# do an UPDATE, not to produce a fully usable object
self._run_on_load(obj)
return obj
class PendingCollection(object):
"""A writable placeholder for an unloaded collection.
Stores items appended to and removed from a collection that has not yet
been loaded. When the collection is loaded, the changes stored in
PendingCollection are applied to it to produce the final result.
"""
def __init__(self):
self.deleted_items = util.IdentitySet()
self.added_items = util.OrderedIdentitySet()
def append(self, value):
if value in self.deleted_items:
self.deleted_items.remove(value)
self.added_items.add(value)
def remove(self, value):
if value in self.added_items:
self.added_items.remove(value)
self.deleted_items.add(value)
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