730 lines
22 KiB
Python
730 lines
22 KiB
Python
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# orm/state.py
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# Copyright (C) 2005-2015 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: http://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 util
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from . import exc as orm_exc, interfaces
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from .path_registry import PathRegistry
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from .base import PASSIVE_NO_RESULT, SQL_OK, NEVER_SET, ATTR_WAS_SET, \
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NO_VALUE, PASSIVE_NO_INITIALIZE, INIT_OK, PASSIVE_OFF
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from . import base
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class InstanceState(interfaces.InspectionAttr):
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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:`.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 = ()
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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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is_instance = True
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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(
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(key, AttributeState(self, key))
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for key in self.manager
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)
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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 \
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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 \
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self._attached
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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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.. seealso::
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:ref:`session_object_states`
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"""
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return self.key is not None and \
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self._attached
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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 \
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not self._attached
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@property
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@util.dependencies("sqlalchemy.orm.session")
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def _attached(self, sessionlib):
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return self.session_id is not None and \
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self.session_id in sessionlib._sessions
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@property
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@util.dependencies("sqlalchemy.orm.session")
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def session(self, sessionlib):
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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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"""
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return sessionlib._state_session(self)
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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.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 transient or 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 mapper(self):
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"""Return the :class:`.Mapper` used for this mapepd 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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def _detach(self):
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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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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]) for k in (
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'committed_state', '_pending_mutations', 'modified',
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'expired', 'callables', 'key', 'parents', 'load_options',
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'class_', 'expired_attributes'
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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 '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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self.__dict__.update([
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(k, state_dict[k]) for k in (
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'key', 'load_options',
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) if k in state_dict
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])
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if 'load_path' in state_dict:
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self.load_path = PathRegistry.\
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deserialize(state_dict['load_path'])
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state_dict['manager'](self, inst, state_dict)
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def _reset(self, dict_, key):
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"""Remove the given attribute and any
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callables associated with it."""
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old = dict_.pop(key, None)
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if old is not None and self.manager[key].impl.collection:
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self.manager[key].impl._invalidate_collection(old)
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self.expired_attributes.discard(key)
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if self.callables:
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self.callables.pop(key, None)
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@classmethod
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def _instance_level_callable_processor(cls, manager, fn, key):
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impl = manager[key].impl
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if impl.collection:
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def _set_callable(state, dict_, row):
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if 'callables' not in state.__dict__:
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state.callables = {}
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old = dict_.pop(key, None)
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if old is not None:
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impl._invalidate_collection(old)
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state.callables[key] = fn
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else:
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def _set_callable(state, dict_, row):
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if 'callables' not in state.__dict__:
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state.callables = {}
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state.callables[key] = fn
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return _set_callable
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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):
|
||
|
|
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:
|
||
|
|
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)
|