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1024 lines
33 KiB
1024 lines
33 KiB
# orm/state.py
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# Copyright (C) 2005-2022 the SQLAlchemy authors and contributors
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# <see AUTHORS file>
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#
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# This module is part of SQLAlchemy and is released under
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# the MIT License: https://www.opensource.org/licenses/mit-license.php
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"""Defines instrumentation of instances.
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This module is usually not directly visible to user applications, but
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defines a large part of the ORM's interactivity.
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"""
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import weakref
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from . import base
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from . import exc as orm_exc
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from . import interfaces
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from .base import ATTR_WAS_SET
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from .base import INIT_OK
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from .base import NEVER_SET
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from .base import NO_VALUE
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from .base import PASSIVE_NO_INITIALIZE
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from .base import PASSIVE_NO_RESULT
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from .base import PASSIVE_OFF
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from .base import SQL_OK
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from .path_registry import PathRegistry
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from .. import exc as sa_exc
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from .. import inspection
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from .. import util
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# late-populated by session.py
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_sessions = None
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# optionally late-provided by sqlalchemy.ext.asyncio.session
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_async_provider = None
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@inspection._self_inspects
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class InstanceState(interfaces.InspectionAttrInfo):
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"""tracks state information at the instance level.
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The :class:`.InstanceState` is a key object used by the
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SQLAlchemy ORM in order to track the state of an object;
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it is created the moment an object is instantiated, typically
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as a result of :term:`instrumentation` which SQLAlchemy applies
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to the ``__init__()`` method of the class.
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:class:`.InstanceState` is also a semi-public object,
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available for runtime inspection as to the state of a
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mapped instance, including information such as its current
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status within a particular :class:`.Session` and details
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about data on individual attributes. The public API
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in order to acquire a :class:`.InstanceState` object
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is to use the :func:`_sa.inspect` system::
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>>> from sqlalchemy import inspect
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>>> insp = inspect(some_mapped_object)
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.. seealso::
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:ref:`core_inspection_toplevel`
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"""
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session_id = None
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key = None
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runid = None
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load_options = util.EMPTY_SET
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load_path = PathRegistry.root
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insert_order = None
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_strong_obj = None
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modified = False
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expired = False
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_deleted = False
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_load_pending = False
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_orphaned_outside_of_session = False
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is_instance = True
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identity_token = None
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_last_known_values = ()
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callables = ()
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"""A namespace where a per-state loader callable can be associated.
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In SQLAlchemy 1.0, this is only used for lazy loaders / deferred
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loaders that were set up via query option.
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Previously, callables was used also to indicate expired attributes
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by storing a link to the InstanceState itself in this dictionary.
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This role is now handled by the expired_attributes set.
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"""
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def __init__(self, obj, manager):
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self.class_ = obj.__class__
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self.manager = manager
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self.obj = weakref.ref(obj, self._cleanup)
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self.committed_state = {}
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self.expired_attributes = set()
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expired_attributes = None
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"""The set of keys which are 'expired' to be loaded by
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the manager's deferred scalar loader, assuming no pending
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changes.
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see also the ``unmodified`` collection which is intersected
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against this set when a refresh operation occurs."""
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@util.memoized_property
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def attrs(self):
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"""Return a namespace representing each attribute on
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the mapped object, including its current value
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and history.
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The returned object is an instance of :class:`.AttributeState`.
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This object allows inspection of the current data
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within an attribute as well as attribute history
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since the last flush.
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"""
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return util.ImmutableProperties(
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dict((key, AttributeState(self, key)) for key in self.manager)
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)
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@property
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def transient(self):
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"""Return ``True`` if the object is :term:`transient`.
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.. seealso::
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:ref:`session_object_states`
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"""
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return self.key is None and not self._attached
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@property
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def pending(self):
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"""Return ``True`` if the object is :term:`pending`.
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.. seealso::
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:ref:`session_object_states`
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"""
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return self.key is None and self._attached
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@property
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def deleted(self):
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"""Return ``True`` if the object is :term:`deleted`.
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An object that is in the deleted state is guaranteed to
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not be within the :attr:`.Session.identity_map` of its parent
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:class:`.Session`; however if the session's transaction is rolled
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back, the object will be restored to the persistent state and
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the identity map.
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.. note::
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The :attr:`.InstanceState.deleted` attribute refers to a specific
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state of the object that occurs between the "persistent" and
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"detached" states; once the object is :term:`detached`, the
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:attr:`.InstanceState.deleted` attribute **no longer returns
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True**; in order to detect that a state was deleted, regardless
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of whether or not the object is associated with a
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:class:`.Session`, use the :attr:`.InstanceState.was_deleted`
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accessor.
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.. versionadded: 1.1
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.. seealso::
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:ref:`session_object_states`
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"""
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return self.key is not None and self._attached and self._deleted
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@property
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def was_deleted(self):
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"""Return True if this object is or was previously in the
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"deleted" state and has not been reverted to persistent.
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This flag returns True once the object was deleted in flush.
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When the object is expunged from the session either explicitly
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or via transaction commit and enters the "detached" state,
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this flag will continue to report True.
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.. versionadded:: 1.1 - added a local method form of
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:func:`.orm.util.was_deleted`.
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.. seealso::
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:attr:`.InstanceState.deleted` - refers to the "deleted" state
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:func:`.orm.util.was_deleted` - standalone function
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:ref:`session_object_states`
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"""
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return self._deleted
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@property
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def persistent(self):
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"""Return ``True`` if the object is :term:`persistent`.
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An object that is in the persistent state is guaranteed to
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be within the :attr:`.Session.identity_map` of its parent
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:class:`.Session`.
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.. versionchanged:: 1.1 The :attr:`.InstanceState.persistent`
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accessor no longer returns True for an object that was
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"deleted" within a flush; use the :attr:`.InstanceState.deleted`
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accessor to detect this state. This allows the "persistent"
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state to guarantee membership in the identity map.
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.. seealso::
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:ref:`session_object_states`
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"""
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return self.key is not None and self._attached and not self._deleted
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@property
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def detached(self):
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"""Return ``True`` if the object is :term:`detached`.
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.. seealso::
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:ref:`session_object_states`
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"""
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return self.key is not None and not self._attached
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@property
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@util.preload_module("sqlalchemy.orm.session")
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def _attached(self):
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return (
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self.session_id is not None
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and self.session_id in util.preloaded.orm_session._sessions
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)
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def _track_last_known_value(self, key):
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"""Track the last known value of a particular key after expiration
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operations.
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.. versionadded:: 1.3
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"""
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if key not in self._last_known_values:
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self._last_known_values = dict(self._last_known_values)
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self._last_known_values[key] = NO_VALUE
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@property
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def session(self):
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"""Return the owning :class:`.Session` for this instance,
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or ``None`` if none available.
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Note that the result here can in some cases be *different*
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from that of ``obj in session``; an object that's been deleted
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will report as not ``in session``, however if the transaction is
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still in progress, this attribute will still refer to that session.
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Only when the transaction is completed does the object become
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fully detached under normal circumstances.
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.. seealso::
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:attr:`_orm.InstanceState.async_session`
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"""
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if self.session_id:
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try:
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return _sessions[self.session_id]
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except KeyError:
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pass
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return None
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@property
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def async_session(self):
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"""Return the owning :class:`_asyncio.AsyncSession` for this instance,
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or ``None`` if none available.
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This attribute is only non-None when the :mod:`sqlalchemy.ext.asyncio`
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API is in use for this ORM object. The returned
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:class:`_asyncio.AsyncSession` object will be a proxy for the
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:class:`_orm.Session` object that would be returned from the
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:attr:`_orm.InstanceState.session` attribute for this
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:class:`_orm.InstanceState`.
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.. versionadded:: 1.4.18
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.. seealso::
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:ref:`asyncio_toplevel`
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"""
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if _async_provider is None:
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return None
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sess = self.session
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if sess is not None:
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return _async_provider(sess)
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else:
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return None
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@property
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def object(self):
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"""Return the mapped object represented by this
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:class:`.InstanceState`."""
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return self.obj()
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@property
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def identity(self):
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"""Return the mapped identity of the mapped object.
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This is the primary key identity as persisted by the ORM
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which can always be passed directly to
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:meth:`_query.Query.get`.
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Returns ``None`` if the object has no primary key identity.
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.. note::
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An object which is :term:`transient` or :term:`pending`
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does **not** have a mapped identity until it is flushed,
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even if its attributes include primary key values.
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"""
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if self.key is None:
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return None
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else:
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return self.key[1]
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@property
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def identity_key(self):
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"""Return the identity key for the mapped object.
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This is the key used to locate the object within
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the :attr:`.Session.identity_map` mapping. It contains
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the identity as returned by :attr:`.identity` within it.
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"""
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# TODO: just change .key to .identity_key across
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# the board ? probably
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return self.key
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@util.memoized_property
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def parents(self):
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return {}
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@util.memoized_property
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def _pending_mutations(self):
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return {}
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@util.memoized_property
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def _empty_collections(self):
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return {}
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@util.memoized_property
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def mapper(self):
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"""Return the :class:`_orm.Mapper` used for this mapped object."""
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return self.manager.mapper
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@property
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def has_identity(self):
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"""Return ``True`` if this object has an identity key.
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This should always have the same value as the
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expression ``state.persistent`` or ``state.detached``.
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"""
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return bool(self.key)
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@classmethod
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def _detach_states(self, states, session, to_transient=False):
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persistent_to_detached = (
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session.dispatch.persistent_to_detached or None
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)
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deleted_to_detached = session.dispatch.deleted_to_detached or None
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pending_to_transient = session.dispatch.pending_to_transient or None
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persistent_to_transient = (
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session.dispatch.persistent_to_transient or None
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)
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for state in states:
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deleted = state._deleted
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pending = state.key is None
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persistent = not pending and not deleted
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state.session_id = None
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if to_transient and state.key:
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del state.key
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if persistent:
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if to_transient:
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if persistent_to_transient is not None:
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persistent_to_transient(session, state)
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elif persistent_to_detached is not None:
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persistent_to_detached(session, state)
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elif deleted and deleted_to_detached is not None:
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deleted_to_detached(session, state)
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elif pending and pending_to_transient is not None:
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pending_to_transient(session, state)
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state._strong_obj = None
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def _detach(self, session=None):
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if session:
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InstanceState._detach_states([self], session)
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else:
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self.session_id = self._strong_obj = None
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def _dispose(self):
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self._detach()
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del self.obj
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def _cleanup(self, ref):
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"""Weakref callback cleanup.
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This callable cleans out the state when it is being garbage
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collected.
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this _cleanup **assumes** that there are no strong refs to us!
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Will not work otherwise!
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"""
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# Python builtins become undefined during interpreter shutdown.
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# Guard against exceptions during this phase, as the method cannot
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# proceed in any case if builtins have been undefined.
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if dict is None:
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return
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instance_dict = self._instance_dict()
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if instance_dict is not None:
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instance_dict._fast_discard(self)
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del self._instance_dict
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# we can't possibly be in instance_dict._modified
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# b.c. this is weakref cleanup only, that set
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# is strong referencing!
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# assert self not in instance_dict._modified
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self.session_id = self._strong_obj = None
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del self.obj
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def obj(self):
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return None
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@property
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def dict(self):
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"""Return the instance dict used by the object.
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Under normal circumstances, this is always synonymous
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with the ``__dict__`` attribute of the mapped object,
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unless an alternative instrumentation system has been
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configured.
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In the case that the actual object has been garbage
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collected, this accessor returns a blank dictionary.
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"""
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o = self.obj()
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if o is not None:
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return base.instance_dict(o)
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else:
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return {}
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def _initialize_instance(*mixed, **kwargs):
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self, instance, args = mixed[0], mixed[1], mixed[2:] # noqa
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manager = self.manager
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manager.dispatch.init(self, args, kwargs)
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try:
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return manager.original_init(*mixed[1:], **kwargs)
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except:
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with util.safe_reraise():
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manager.dispatch.init_failure(self, args, kwargs)
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def get_history(self, key, passive):
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return self.manager[key].impl.get_history(self, self.dict, passive)
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def get_impl(self, key):
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return self.manager[key].impl
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def _get_pending_mutation(self, key):
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if key not in self._pending_mutations:
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self._pending_mutations[key] = PendingCollection()
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return self._pending_mutations[key]
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def __getstate__(self):
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state_dict = {"instance": self.obj()}
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state_dict.update(
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(k, self.__dict__[k])
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for k in (
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"committed_state",
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"_pending_mutations",
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"modified",
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"expired",
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"callables",
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"key",
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"parents",
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"load_options",
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"class_",
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"expired_attributes",
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"info",
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)
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if k in self.__dict__
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)
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if self.load_path:
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state_dict["load_path"] = self.load_path.serialize()
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state_dict["manager"] = self.manager._serialize(self, state_dict)
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return state_dict
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def __setstate__(self, state_dict):
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inst = state_dict["instance"]
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if inst is not None:
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self.obj = weakref.ref(inst, self._cleanup)
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self.class_ = inst.__class__
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else:
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# None being possible here generally new as of 0.7.4
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# due to storage of state in "parents". "class_"
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# also new.
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self.obj = None
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self.class_ = state_dict["class_"]
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self.committed_state = state_dict.get("committed_state", {})
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self._pending_mutations = state_dict.get("_pending_mutations", {})
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self.parents = state_dict.get("parents", {})
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self.modified = state_dict.get("modified", False)
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self.expired = state_dict.get("expired", False)
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if "info" in state_dict:
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self.info.update(state_dict["info"])
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if "callables" in state_dict:
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self.callables = state_dict["callables"]
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try:
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self.expired_attributes = state_dict["expired_attributes"]
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except KeyError:
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self.expired_attributes = set()
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# 0.9 and earlier compat
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for k in list(self.callables):
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if self.callables[k] is self:
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self.expired_attributes.add(k)
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del self.callables[k]
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else:
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if "expired_attributes" in state_dict:
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self.expired_attributes = state_dict["expired_attributes"]
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else:
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self.expired_attributes = set()
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self.__dict__.update(
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[
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(k, state_dict[k])
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for k in ("key", "load_options")
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if k in state_dict
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]
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)
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if self.key:
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try:
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self.identity_token = self.key[2]
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except IndexError:
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# 1.1 and earlier compat before identity_token
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assert len(self.key) == 2
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self.key = self.key + (None,)
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self.identity_token = None
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if "load_path" in state_dict:
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self.load_path = PathRegistry.deserialize(state_dict["load_path"])
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|
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._loader_impls]
|
|
)
|
|
|
|
if self.callables:
|
|
# the per state loader callables we can remove here are
|
|
# LoadDeferredColumns, which undefers a column at the instance
|
|
# level that is mapped with deferred, and LoadLazyAttribute,
|
|
# which lazy loads a relationship at the instance level that
|
|
# is mapped with "noload" or perhaps "immediateload".
|
|
# Before 1.4, only column-based
|
|
# attributes could be considered to be "expired", so here they
|
|
# were the only ones "unexpired", which means to make them deferred
|
|
# again. For the moment, as of 1.4 we also apply the same
|
|
# treatment relationships now, that is, an instance level lazy
|
|
# loader is reset in the same way as a column loader.
|
|
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
|
|
|
|
if self._last_known_values:
|
|
self._last_known_values.update(
|
|
(k, dict_[k]) for k in self._last_known_values if k in dict_
|
|
)
|
|
|
|
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, NO_VALUE)
|
|
if impl.collection and old is not NO_VALUE:
|
|
impl._invalidate_collection(old)
|
|
|
|
if (
|
|
self._last_known_values
|
|
and key in self._last_known_values
|
|
and old is not NO_VALUE
|
|
):
|
|
self._last_known_values[key] = 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)
|
|
toload = toload.difference(
|
|
attr
|
|
for attr in toload
|
|
if not self.manager[attr].impl.load_on_unexpire
|
|
)
|
|
|
|
self.manager.expired_attribute_loader(self, toload, passive)
|
|
|
|
# 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_expirable(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 self.unloaded
|
|
|
|
@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, is_userland=False
|
|
):
|
|
if attr:
|
|
if not attr.send_modified_events:
|
|
return
|
|
if is_userland and attr.key not in dict_:
|
|
raise sa_exc.InvalidRequestError(
|
|
"Can't flag attribute '%s' modified; it's not present in "
|
|
"the object state" % attr.key
|
|
)
|
|
if attr.key not in self.committed_state or is_userland:
|
|
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
|
|
|
|
if attr.key in self._last_known_values:
|
|
self._last_known_values[attr.key] = NO_VALUE
|
|
|
|
# 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:
|
|
has_modified = bool(instance_dict._modified)
|
|
instance_dict._modified.add(self)
|
|
else:
|
|
has_modified = False
|
|
|
|
# only create _strong_obj link if attached
|
|
# to a session
|
|
|
|
inst = self.obj()
|
|
if self.session_id:
|
|
self._strong_obj = inst
|
|
|
|
# if identity map already had modified objects,
|
|
# assume autobegin already occurred, else check
|
|
# for autobegin
|
|
if not has_modified:
|
|
# inline of autobegin, to ensure session transaction
|
|
# snapshot is established
|
|
try:
|
|
session = _sessions[self.session_id]
|
|
except KeyError:
|
|
pass
|
|
else:
|
|
if session._transaction is None:
|
|
session._autobegin()
|
|
|
|
if inst is None and attr:
|
|
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.
|
|
|
|
.. note::
|
|
|
|
The attribute history system tracks changes on a **per flush
|
|
basis**. Each time the :class:`.Session` is flushed, the history
|
|
of each attribute is reset to empty. The :class:`.Session` by
|
|
default autoflushes each time a :class:`_query.Query` is invoked.
|
|
For
|
|
options on how to control this, see :ref:`session_flushing`.
|
|
|
|
|
|
.. 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.
|
|
|
|
.. note::
|
|
|
|
The attribute history system tracks changes on a **per flush
|
|
basis**. Each time the :class:`.Session` is flushed, the history
|
|
of each attribute is reset to empty. The :class:`.Session` by
|
|
default autoflushes each time a :class:`_query.Query` is invoked.
|
|
For
|
|
options on how to control this, see :ref:`session_flushing`.
|
|
|
|
.. 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)
|