848 lines
27 KiB
Python
848 lines
27 KiB
Python
# orm/state.py
|
|
# Copyright (C) 2005-2017 the SQLAlchemy authors and contributors
|
|
# <see AUTHORS file>
|
|
#
|
|
# This module is part of SQLAlchemy and is released under
|
|
# the MIT License: http://www.opensource.org/licenses/mit-license.php
|
|
|
|
"""Defines instrumentation of instances.
|
|
|
|
This module is usually not directly visible to user applications, but
|
|
defines a large part of the ORM's interactivity.
|
|
|
|
"""
|
|
|
|
import weakref
|
|
from .. import util
|
|
from .. import inspection
|
|
from . import exc as orm_exc, interfaces
|
|
from .path_registry import PathRegistry
|
|
from .base import PASSIVE_NO_RESULT, SQL_OK, NEVER_SET, ATTR_WAS_SET, \
|
|
NO_VALUE, PASSIVE_NO_INITIALIZE, INIT_OK, PASSIVE_OFF
|
|
from . import base
|
|
|
|
|
|
@inspection._self_inspects
|
|
class InstanceState(interfaces.InspectionAttr):
|
|
"""tracks state information at the instance level.
|
|
|
|
The :class:`.InstanceState` is a key object used by the
|
|
SQLAlchemy ORM in order to track the state of an object;
|
|
it is created the moment an object is instantiated, typically
|
|
as a result of :term:`instrumentation` which SQLAlchemy applies
|
|
to the ``__init__()`` method of the class.
|
|
|
|
:class:`.InstanceState` is also a semi-public object,
|
|
available for runtime inspection as to the state of a
|
|
mapped instance, including information such as its current
|
|
status within a particular :class:`.Session` and details
|
|
about data on individual attributes. The public API
|
|
in order to acquire a :class:`.InstanceState` object
|
|
is to use the :func:`.inspect` system::
|
|
|
|
>>> from sqlalchemy import inspect
|
|
>>> insp = inspect(some_mapped_object)
|
|
|
|
.. seealso::
|
|
|
|
:ref:`core_inspection_toplevel`
|
|
|
|
"""
|
|
|
|
session_id = None
|
|
key = None
|
|
runid = None
|
|
load_options = util.EMPTY_SET
|
|
load_path = ()
|
|
insert_order = None
|
|
_strong_obj = None
|
|
modified = False
|
|
expired = False
|
|
_deleted = False
|
|
_load_pending = False
|
|
is_instance = True
|
|
|
|
callables = ()
|
|
"""A namespace where a per-state loader callable can be associated.
|
|
|
|
In SQLAlchemy 1.0, this is only used for lazy loaders / deferred
|
|
loaders that were set up via query option.
|
|
|
|
Previously, callables was used also to indicate expired attributes
|
|
by storing a link to the InstanceState itself in this dictionary.
|
|
This role is now handled by the expired_attributes set.
|
|
|
|
"""
|
|
|
|
def __init__(self, obj, manager):
|
|
self.class_ = obj.__class__
|
|
self.manager = manager
|
|
self.obj = weakref.ref(obj, self._cleanup)
|
|
self.committed_state = {}
|
|
self.expired_attributes = set()
|
|
|
|
expired_attributes = None
|
|
"""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."""
|
|
|
|
@util.memoized_property
|
|
def attrs(self):
|
|
"""Return a namespace representing each attribute on
|
|
the mapped object, including its current value
|
|
and history.
|
|
|
|
The returned object is an instance of :class:`.AttributeState`.
|
|
This object allows inspection of the current data
|
|
within an attribute as well as attribute history
|
|
since the last flush.
|
|
|
|
"""
|
|
return util.ImmutableProperties(
|
|
dict(
|
|
(key, AttributeState(self, key))
|
|
for key in self.manager
|
|
)
|
|
)
|
|
|
|
@property
|
|
def transient(self):
|
|
"""Return true if the object is :term:`transient`.
|
|
|
|
.. seealso::
|
|
|
|
:ref:`session_object_states`
|
|
|
|
"""
|
|
return self.key is None and \
|
|
not self._attached
|
|
|
|
@property
|
|
def pending(self):
|
|
"""Return true if the object is :term:`pending`.
|
|
|
|
|
|
.. seealso::
|
|
|
|
:ref:`session_object_states`
|
|
|
|
"""
|
|
return self.key is None and \
|
|
self._attached
|
|
|
|
@property
|
|
def deleted(self):
|
|
"""Return true if the object is :term:`deleted`.
|
|
|
|
An object that is in the deleted state is guaranteed to
|
|
not be within the :attr:`.Session.identity_map` of its parent
|
|
:class:`.Session`; however if the session's transaction is rolled
|
|
back, the object will be restored to the persistent state and
|
|
the identity map.
|
|
|
|
.. note::
|
|
|
|
The :attr:`.InstanceState.deleted` attribute refers to a specific
|
|
state of the object that occurs between the "persistent" and
|
|
"detached" states; once the object is :term:`detached`, the
|
|
:attr:`.InstanceState.deleted` attribute **no longer returns
|
|
True**; in order to detect that a state was deleted, regardless
|
|
of whether or not the object is associated with a :class:`.Session`,
|
|
use the :attr:`.InstanceState.was_deleted` accessor.
|
|
|
|
.. versionadded: 1.1
|
|
|
|
.. seealso::
|
|
|
|
:ref:`session_object_states`
|
|
|
|
"""
|
|
return self.key is not None and \
|
|
self._attached and self._deleted
|
|
|
|
@property
|
|
def was_deleted(self):
|
|
"""Return True if this object is or was previously in the
|
|
"deleted" state and has not been reverted to persistent.
|
|
|
|
This flag returns True once the object was deleted in flush.
|
|
When the object is expunged from the session either explicitly
|
|
or via transaction commit and enters the "detached" state,
|
|
this flag will continue to report True.
|
|
|
|
.. versionadded:: 1.1 - added a local method form of
|
|
:func:`.orm.util.was_deleted`.
|
|
|
|
.. seealso::
|
|
|
|
:attr:`.InstanceState.deleted` - refers to the "deleted" state
|
|
|
|
:func:`.orm.util.was_deleted` - standalone function
|
|
|
|
:ref:`session_object_states`
|
|
|
|
"""
|
|
return self._deleted
|
|
|
|
@property
|
|
def persistent(self):
|
|
"""Return true if the object is :term:`persistent`.
|
|
|
|
An object that is in the persistent state is guaranteed to
|
|
be within the :attr:`.Session.identity_map` of its parent
|
|
:class:`.Session`.
|
|
|
|
.. versionchanged:: 1.1 The :attr:`.InstanceState.persistent`
|
|
accessor no longer returns True for an object that was
|
|
"deleted" within a flush; use the :attr:`.InstanceState.deleted`
|
|
accessor to detect this state. This allows the "persistent"
|
|
state to guarantee membership in the identity map.
|
|
|
|
.. seealso::
|
|
|
|
:ref:`session_object_states`
|
|
|
|
"""
|
|
return self.key is not None and \
|
|
self._attached and not self._deleted
|
|
|
|
@property
|
|
def detached(self):
|
|
"""Return true if the object is :term:`detached`.
|
|
|
|
.. seealso::
|
|
|
|
:ref:`session_object_states`
|
|
|
|
"""
|
|
return self.key is not None and not self._attached
|
|
|
|
@property
|
|
@util.dependencies("sqlalchemy.orm.session")
|
|
def _attached(self, sessionlib):
|
|
return self.session_id is not None and \
|
|
self.session_id in sessionlib._sessions
|
|
|
|
@property
|
|
@util.dependencies("sqlalchemy.orm.session")
|
|
def session(self, sessionlib):
|
|
"""Return the owning :class:`.Session` for this instance,
|
|
or ``None`` if none available.
|
|
|
|
Note that the result here can in some cases be *different*
|
|
from that of ``obj in session``; an object that's been deleted
|
|
will report as not ``in session``, however if the transaction is
|
|
still in progress, this attribute will still refer to that session.
|
|
Only when the transaction is completed does the object become
|
|
fully detached under normal circumstances.
|
|
|
|
"""
|
|
return sessionlib._state_session(self)
|
|
|
|
@property
|
|
def object(self):
|
|
"""Return the mapped object represented by this
|
|
:class:`.InstanceState`."""
|
|
return self.obj()
|
|
|
|
@property
|
|
def identity(self):
|
|
"""Return the mapped identity of the mapped object.
|
|
This is the primary key identity as persisted by the ORM
|
|
which can always be passed directly to
|
|
:meth:`.Query.get`.
|
|
|
|
Returns ``None`` if the object has no primary key identity.
|
|
|
|
.. note::
|
|
An object which is :term:`transient` or :term:`pending`
|
|
does **not** have a mapped identity until it is flushed,
|
|
even if its attributes include primary key values.
|
|
|
|
"""
|
|
if self.key is None:
|
|
return None
|
|
else:
|
|
return self.key[1]
|
|
|
|
@property
|
|
def identity_key(self):
|
|
"""Return the identity key for the mapped object.
|
|
|
|
This is the key used to locate the object within
|
|
the :attr:`.Session.identity_map` mapping. It contains
|
|
the identity as returned by :attr:`.identity` within it.
|
|
|
|
|
|
"""
|
|
# TODO: just change .key to .identity_key across
|
|
# the board ? probably
|
|
return self.key
|
|
|
|
@util.memoized_property
|
|
def parents(self):
|
|
return {}
|
|
|
|
@util.memoized_property
|
|
def _pending_mutations(self):
|
|
return {}
|
|
|
|
@util.memoized_property
|
|
def mapper(self):
|
|
"""Return the :class:`.Mapper` used for this mapepd object."""
|
|
return self.manager.mapper
|
|
|
|
@property
|
|
def has_identity(self):
|
|
"""Return ``True`` if this object has an identity key.
|
|
|
|
This should always have the same value as the
|
|
expression ``state.persistent or state.detached``.
|
|
|
|
"""
|
|
return bool(self.key)
|
|
|
|
@classmethod
|
|
def _detach_states(self, states, session, to_transient=False):
|
|
persistent_to_detached = \
|
|
session.dispatch.persistent_to_detached or None
|
|
deleted_to_detached = \
|
|
session.dispatch.deleted_to_detached or None
|
|
pending_to_transient = \
|
|
session.dispatch.pending_to_transient or None
|
|
persistent_to_transient = \
|
|
session.dispatch.persistent_to_transient or None
|
|
|
|
for state in states:
|
|
deleted = state._deleted
|
|
pending = state.key is None
|
|
persistent = not pending and not deleted
|
|
|
|
state.session_id = None
|
|
|
|
if to_transient and state.key:
|
|
del state.key
|
|
if persistent:
|
|
if to_transient:
|
|
if persistent_to_transient is not None:
|
|
obj = state.obj()
|
|
if obj is not None:
|
|
persistent_to_transient(session, obj)
|
|
elif persistent_to_detached is not None:
|
|
obj = state.obj()
|
|
if obj is not None:
|
|
persistent_to_detached(session, obj)
|
|
elif deleted and deleted_to_detached is not None:
|
|
obj = state.obj()
|
|
if obj is not None:
|
|
deleted_to_detached(session, obj)
|
|
elif pending and pending_to_transient is not None:
|
|
obj = state.obj()
|
|
if obj is not None:
|
|
pending_to_transient(session, obj)
|
|
|
|
state._strong_obj = None
|
|
|
|
def _detach(self, session=None):
|
|
if session:
|
|
InstanceState._detach_states([self], session)
|
|
else:
|
|
self.session_id = self._strong_obj = None
|
|
|
|
def _dispose(self):
|
|
self._detach()
|
|
del self.obj
|
|
|
|
def _cleanup(self, ref):
|
|
"""Weakref callback cleanup.
|
|
|
|
This callable cleans out the state when it is being garbage
|
|
collected.
|
|
|
|
this _cleanup **assumes** that there are no strong refs to us!
|
|
Will not work otherwise!
|
|
|
|
"""
|
|
instance_dict = self._instance_dict()
|
|
if instance_dict is not None:
|
|
instance_dict._fast_discard(self)
|
|
del self._instance_dict
|
|
|
|
# we can't possibly be in instance_dict._modified
|
|
# b.c. this is weakref cleanup only, that set
|
|
# is strong referencing!
|
|
# assert self not in instance_dict._modified
|
|
|
|
self.session_id = self._strong_obj = None
|
|
del self.obj
|
|
|
|
def obj(self):
|
|
return None
|
|
|
|
@property
|
|
def dict(self):
|
|
"""Return the instance dict used by the object.
|
|
|
|
Under normal circumstances, this is always synonymous
|
|
with the ``__dict__`` attribute of the mapped object,
|
|
unless an alternative instrumentation system has been
|
|
configured.
|
|
|
|
In the case that the actual object has been garbage
|
|
collected, this accessor returns a blank dictionary.
|
|
|
|
"""
|
|
o = self.obj()
|
|
if o is not None:
|
|
return base.instance_dict(o)
|
|
else:
|
|
return {}
|
|
|
|
def _initialize_instance(*mixed, **kwargs):
|
|
self, instance, args = mixed[0], mixed[1], mixed[2:] # noqa
|
|
manager = self.manager
|
|
|
|
manager.dispatch.init(self, args, kwargs)
|
|
|
|
try:
|
|
return manager.original_init(*mixed[1:], **kwargs)
|
|
except:
|
|
with util.safe_reraise():
|
|
manager.dispatch.init_failure(self, args, kwargs)
|
|
|
|
def get_history(self, key, passive):
|
|
return self.manager[key].impl.get_history(self, self.dict, passive)
|
|
|
|
def get_impl(self, key):
|
|
return self.manager[key].impl
|
|
|
|
def _get_pending_mutation(self, key):
|
|
if key not in self._pending_mutations:
|
|
self._pending_mutations[key] = PendingCollection()
|
|
return self._pending_mutations[key]
|
|
|
|
def __getstate__(self):
|
|
state_dict = {'instance': self.obj()}
|
|
state_dict.update(
|
|
(k, self.__dict__[k]) for k in (
|
|
'committed_state', '_pending_mutations', 'modified',
|
|
'expired', 'callables', 'key', 'parents', 'load_options',
|
|
'class_', 'expired_attributes'
|
|
) if k in self.__dict__
|
|
)
|
|
if self.load_path:
|
|
state_dict['load_path'] = self.load_path.serialize()
|
|
|
|
state_dict['manager'] = self.manager._serialize(self, state_dict)
|
|
|
|
return state_dict
|
|
|
|
def __setstate__(self, state_dict):
|
|
inst = state_dict['instance']
|
|
if inst is not None:
|
|
self.obj = weakref.ref(inst, self._cleanup)
|
|
self.class_ = inst.__class__
|
|
else:
|
|
# None being possible here generally new as of 0.7.4
|
|
# due to storage of state in "parents". "class_"
|
|
# also new.
|
|
self.obj = None
|
|
self.class_ = state_dict['class_']
|
|
|
|
self.committed_state = state_dict.get('committed_state', {})
|
|
self._pending_mutations = state_dict.get('_pending_mutations', {})
|
|
self.parents = state_dict.get('parents', {})
|
|
self.modified = state_dict.get('modified', False)
|
|
self.expired = state_dict.get('expired', False)
|
|
if 'callables' in state_dict:
|
|
self.callables = state_dict['callables']
|
|
|
|
try:
|
|
self.expired_attributes = state_dict['expired_attributes']
|
|
except KeyError:
|
|
self.expired_attributes = set()
|
|
# 0.9 and earlier compat
|
|
for k in list(self.callables):
|
|
if self.callables[k] is self:
|
|
self.expired_attributes.add(k)
|
|
del self.callables[k]
|
|
|
|
self.__dict__.update([
|
|
(k, state_dict[k]) for k in (
|
|
'key', 'load_options',
|
|
) if k in state_dict
|
|
])
|
|
|
|
if 'load_path' in state_dict:
|
|
self.load_path = PathRegistry.\
|
|
deserialize(state_dict['load_path'])
|
|
|
|
state_dict['manager'](self, inst, state_dict)
|
|
|
|
def _reset(self, dict_, key):
|
|
"""Remove the given attribute and any
|
|
callables associated with it."""
|
|
|
|
old = dict_.pop(key, None)
|
|
if old is not None and self.manager[key].impl.collection:
|
|
self.manager[key].impl._invalidate_collection(old)
|
|
self.expired_attributes.discard(key)
|
|
if self.callables:
|
|
self.callables.pop(key, None)
|
|
|
|
def _copy_callables(self, from_):
|
|
if 'callables' in from_.__dict__:
|
|
self.callables = dict(from_.callables)
|
|
|
|
@classmethod
|
|
def _instance_level_callable_processor(cls, manager, fn, key):
|
|
impl = manager[key].impl
|
|
if impl.collection:
|
|
def _set_callable(state, dict_, row):
|
|
if 'callables' not in state.__dict__:
|
|
state.callables = {}
|
|
old = dict_.pop(key, None)
|
|
if old is not None:
|
|
impl._invalidate_collection(old)
|
|
state.callables[key] = fn
|
|
else:
|
|
def _set_callable(state, dict_, row):
|
|
if 'callables' not in state.__dict__:
|
|
state.callables = {}
|
|
state.callables[key] = fn
|
|
return _set_callable
|
|
|
|
def _expire(self, dict_, modified_set):
|
|
self.expired = True
|
|
|
|
if self.modified:
|
|
modified_set.discard(self)
|
|
self.committed_state.clear()
|
|
self.modified = False
|
|
|
|
self._strong_obj = None
|
|
|
|
if '_pending_mutations' in self.__dict__:
|
|
del self.__dict__['_pending_mutations']
|
|
|
|
if 'parents' in self.__dict__:
|
|
del self.__dict__['parents']
|
|
|
|
self.expired_attributes.update(
|
|
[impl.key for impl in self.manager._scalar_loader_impls
|
|
if impl.expire_missing or impl.key in dict_]
|
|
)
|
|
|
|
if self.callables:
|
|
for k in self.expired_attributes.intersection(self.callables):
|
|
del self.callables[k]
|
|
|
|
for k in self.manager._collection_impl_keys.intersection(dict_):
|
|
collection = dict_.pop(k)
|
|
collection._sa_adapter.invalidated = True
|
|
|
|
for key in self.manager._all_key_set.intersection(dict_):
|
|
del dict_[key]
|
|
|
|
self.manager.dispatch.expire(self, None)
|
|
|
|
def _expire_attributes(self, dict_, attribute_names, no_loader=False):
|
|
pending = self.__dict__.get('_pending_mutations', None)
|
|
|
|
callables = self.callables
|
|
|
|
for key in attribute_names:
|
|
impl = self.manager[key].impl
|
|
if impl.accepts_scalar_loader:
|
|
if no_loader and (
|
|
impl.callable_ or
|
|
key in callables
|
|
):
|
|
continue
|
|
|
|
self.expired_attributes.add(key)
|
|
if callables and key in callables:
|
|
del callables[key]
|
|
old = dict_.pop(key, None)
|
|
if impl.collection and old is not None:
|
|
impl._invalidate_collection(old)
|
|
|
|
self.committed_state.pop(key, None)
|
|
if pending:
|
|
pending.pop(key, None)
|
|
|
|
self.manager.dispatch.expire(self, attribute_names)
|
|
|
|
def _load_expired(self, state, passive):
|
|
"""__call__ allows the InstanceState to act as a deferred
|
|
callable for loading expired attributes, which is also
|
|
serializable (picklable).
|
|
|
|
"""
|
|
|
|
if not passive & SQL_OK:
|
|
return 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.
|
|
self.expired_attributes.clear()
|
|
|
|
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)
|
|
|
|
def unmodified_intersection(self, keys):
|
|
"""Return self.unmodified.intersection(keys)."""
|
|
|
|
return set(keys).intersection(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 _unloaded_non_object(self):
|
|
return self.unloaded.intersection(
|
|
attr for attr in self.manager
|
|
if self.manager[attr].impl.accepts_scalar_loader
|
|
)
|
|
|
|
def _instance_dict(self):
|
|
return None
|
|
|
|
def _modified_event(
|
|
self, dict_, attr, previous, collection=False, force=False):
|
|
if not attr.send_modified_events:
|
|
return
|
|
if attr.key not in self.committed_state or force:
|
|
if collection:
|
|
if previous is NEVER_SET:
|
|
if attr.key in dict_:
|
|
previous = dict_[attr.key]
|
|
|
|
if previous not in (None, NO_VALUE, NEVER_SET):
|
|
previous = attr.copy(previous)
|
|
|
|
self.committed_state[attr.key] = previous
|
|
|
|
# assert self._strong_obj is None or self.modified
|
|
|
|
if (self.session_id and self._strong_obj is None) \
|
|
or not self.modified:
|
|
self.modified = True
|
|
instance_dict = self._instance_dict()
|
|
if instance_dict:
|
|
instance_dict._modified.add(self)
|
|
|
|
# only create _strong_obj link if attached
|
|
# to a session
|
|
|
|
inst = self.obj()
|
|
if self.session_id:
|
|
self._strong_obj = inst
|
|
|
|
if inst is None:
|
|
raise orm_exc.ObjectDereferencedError(
|
|
"Can't emit change event for attribute '%s' - "
|
|
"parent object of type %s has been garbage "
|
|
"collected."
|
|
% (
|
|
self.manager[attr.key],
|
|
base.state_class_str(self)
|
|
))
|
|
|
|
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.
|
|
|
|
"""
|
|
for key in keys:
|
|
self.committed_state.pop(key, None)
|
|
|
|
self.expired = False
|
|
|
|
self.expired_attributes.difference_update(
|
|
set(keys).intersection(dict_))
|
|
|
|
# the per-keys commit removes object-level callables,
|
|
# while that of commit_all does not. it's not clear
|
|
# if this behavior has a clear rationale, however tests do
|
|
# ensure this is what it does.
|
|
if self.callables:
|
|
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 for scalar attributes loaded are removed.
|
|
- lazy load callables for objects / collections *stay*
|
|
|
|
Attributes marked as "expired" can potentially remain
|
|
"expired" after this step if a value was not populated in state.dict.
|
|
|
|
"""
|
|
self._commit_all_states([(self, dict_)], instance_dict)
|
|
|
|
@classmethod
|
|
def _commit_all_states(self, iter, instance_dict=None):
|
|
"""Mass / highly inlined version of commit_all()."""
|
|
|
|
for state, dict_ in iter:
|
|
state_dict = state.__dict__
|
|
|
|
state.committed_state.clear()
|
|
|
|
if '_pending_mutations' in state_dict:
|
|
del state_dict['_pending_mutations']
|
|
|
|
state.expired_attributes.difference_update(dict_)
|
|
|
|
if instance_dict and state.modified:
|
|
instance_dict._modified.discard(state)
|
|
|
|
state.modified = state.expired = False
|
|
state._strong_obj = None
|
|
|
|
|
|
class AttributeState(object):
|
|
"""Provide an inspection interface corresponding
|
|
to a particular attribute on a particular mapped object.
|
|
|
|
The :class:`.AttributeState` object is accessed
|
|
via the :attr:`.InstanceState.attrs` collection
|
|
of a particular :class:`.InstanceState`::
|
|
|
|
from sqlalchemy import inspect
|
|
|
|
insp = inspect(some_mapped_object)
|
|
attr_state = insp.attrs.some_attribute
|
|
|
|
"""
|
|
|
|
def __init__(self, state, key):
|
|
self.state = state
|
|
self.key = key
|
|
|
|
@property
|
|
def loaded_value(self):
|
|
"""The current value of this attribute as loaded from the database.
|
|
|
|
If the value has not been loaded, or is otherwise not present
|
|
in the object's dictionary, returns NO_VALUE.
|
|
|
|
"""
|
|
return self.state.dict.get(self.key, NO_VALUE)
|
|
|
|
@property
|
|
def value(self):
|
|
"""Return the value of this attribute.
|
|
|
|
This operation is equivalent to accessing the object's
|
|
attribute directly or via ``getattr()``, and will fire
|
|
off any pending loader callables if needed.
|
|
|
|
"""
|
|
return self.state.manager[self.key].__get__(
|
|
self.state.obj(), self.state.class_)
|
|
|
|
@property
|
|
def history(self):
|
|
"""Return the current pre-flush change history for
|
|
this attribute, via the :class:`.History` interface.
|
|
|
|
This method will **not** emit loader callables if the value of the
|
|
attribute is unloaded.
|
|
|
|
.. seealso::
|
|
|
|
:meth:`.AttributeState.load_history` - retrieve history
|
|
using loader callables if the value is not locally present.
|
|
|
|
:func:`.attributes.get_history` - underlying function
|
|
|
|
"""
|
|
return self.state.get_history(self.key,
|
|
PASSIVE_NO_INITIALIZE)
|
|
|
|
def load_history(self):
|
|
"""Return the current pre-flush change history for
|
|
this attribute, via the :class:`.History` interface.
|
|
|
|
This method **will** emit loader callables if the value of the
|
|
attribute is unloaded.
|
|
|
|
.. seealso::
|
|
|
|
:attr:`.AttributeState.history`
|
|
|
|
:func:`.attributes.get_history` - underlying function
|
|
|
|
.. versionadded:: 0.9.0
|
|
|
|
"""
|
|
return self.state.get_history(self.key,
|
|
PASSIVE_OFF ^ INIT_OK)
|
|
|
|
|
|
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)
|
|
else:
|
|
self.added_items.add(value)
|
|
|
|
def remove(self, value):
|
|
if value in self.added_items:
|
|
self.added_items.remove(value)
|
|
else:
|
|
self.deleted_items.add(value)
|