618 lines
19 KiB
Python
618 lines
19 KiB
Python
# orm/state.py
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# Copyright (C) 2005-2014 the SQLAlchemy authors and contributors <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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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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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.callables = {}
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self.committed_state = {}
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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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"""
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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 transient."""
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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 pending."""
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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 persistent."""
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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 detached."""
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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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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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instance_dict = self._instance_dict()
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if instance_dict:
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instance_dict.discard(self)
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self.callables = {}
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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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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:]
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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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manager.dispatch.init_failure(self, args, kwargs)
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raise
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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', 'expired',
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'callables', 'key', 'parents', 'load_options',
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'class_',
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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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self.callables = state_dict.get('callables', {})
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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 _initialize(self, key):
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"""Set this attribute to an empty value or collection,
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based on the AttributeImpl in use."""
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self.manager.get_impl(key).initialize(self, self.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.callables.pop(key, None)
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def _expire_attribute_pre_commit(self, dict_, key):
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"""a fast expire that can be called by column loaders during a load.
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The additional bookkeeping is finished up in commit_all().
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Should only be called for scalar attributes.
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This method is actually called a lot with joined-table
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loading, when the second table isn't present in the result.
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"""
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dict_.pop(key, None)
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self.callables[key] = self
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@classmethod
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def _row_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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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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state.callables[key] = fn
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return _set_callable
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def _expire(self, dict_, modified_set):
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self.expired = True
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if self.modified:
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modified_set.discard(self)
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self.modified = False
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self._strong_obj = None
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self.committed_state.clear()
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InstanceState._pending_mutations._reset(self)
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# clear out 'parents' collection. not
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# entirely clear how we can best determine
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# which to remove, or not.
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InstanceState.parents._reset(self)
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for key in self.manager:
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impl = self.manager[key].impl
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if impl.accepts_scalar_loader and \
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(impl.expire_missing or key in dict_):
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self.callables[key] = self
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old = dict_.pop(key, None)
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if impl.collection and old is not None:
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impl._invalidate_collection(old)
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self.manager.dispatch.expire(self, None)
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def _expire_attributes(self, dict_, attribute_names):
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pending = self.__dict__.get('_pending_mutations', None)
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for key in attribute_names:
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impl = self.manager[key].impl
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if impl.accepts_scalar_loader:
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self.callables[key] = self
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old = dict_.pop(key, None)
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if impl.collection and old is not None:
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impl._invalidate_collection(old)
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self.committed_state.pop(key, None)
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if pending:
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pending.pop(key, None)
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self.manager.dispatch.expire(self, attribute_names)
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def __call__(self, state, passive):
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"""__call__ allows the InstanceState to act as a deferred
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callable for loading expired attributes, which is also
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serializable (picklable).
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"""
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if not passive & SQL_OK:
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return PASSIVE_NO_RESULT
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toload = self.expired_attributes.\
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intersection(self.unmodified)
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self.manager.deferred_scalar_loader(self, toload)
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# if the loader failed, or this
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# instance state didn't have an identity,
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# the attributes still might be in the callables
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# dict. ensure they are removed.
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for k in toload.intersection(self.callables):
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del self.callables[k]
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return ATTR_WAS_SET
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@property
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def unmodified(self):
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"""Return the set of keys which have no uncommitted changes"""
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return set(self.manager).difference(self.committed_state)
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def unmodified_intersection(self, keys):
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"""Return self.unmodified.intersection(keys)."""
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return set(keys).intersection(self.manager).\
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difference(self.committed_state)
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@property
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def unloaded(self):
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"""Return the set of keys which do not have a loaded value.
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This includes expired attributes and any other attribute that
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was never populated or modified.
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"""
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return set(self.manager).\
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difference(self.committed_state).\
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difference(self.dict)
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@property
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def _unloaded_non_object(self):
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return self.unloaded.intersection(
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attr for attr in self.manager
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if self.manager[attr].impl.accepts_scalar_loader
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)
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@property
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def expired_attributes(self):
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"""Return 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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"""
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return set([k for k, v in self.callables.items() if v is self])
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def _instance_dict(self):
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return None
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def _modified_event(self, dict_, attr, previous, collection=False, force=False):
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if not attr.send_modified_events:
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return
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if attr.key not in self.committed_state or force:
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if collection:
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if previous is NEVER_SET:
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if attr.key in dict_:
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previous = dict_[attr.key]
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if previous not in (None, NO_VALUE, NEVER_SET):
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previous = attr.copy(previous)
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self.committed_state[attr.key] = previous
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# assert self._strong_obj is None or self.modified
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if (self.session_id and self._strong_obj is None) \
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or not self.modified:
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instance_dict = self._instance_dict()
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if instance_dict:
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instance_dict._modified.add(self)
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# only create _strong_obj link if attached
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# to a session
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inst = self.obj()
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if self.session_id:
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self._strong_obj = inst
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if inst is None:
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raise orm_exc.ObjectDereferencedError(
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"Can't emit change event for attribute '%s' - "
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"parent object of type %s has been garbage "
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"collected."
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% (
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self.manager[attr.key],
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base.state_class_str(self)
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))
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self.modified = True
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def _commit(self, dict_, keys):
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"""Commit attributes.
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This is used by a partial-attribute load operation to mark committed
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those attributes which were refreshed from the database.
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Attributes marked as "expired" can potentially remain "expired" after
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this step if a value was not populated in state.dict.
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"""
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for key in keys:
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self.committed_state.pop(key, None)
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self.expired = False
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for key in set(self.callables).\
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intersection(keys).\
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intersection(dict_):
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del self.callables[key]
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def _commit_all(self, dict_, instance_dict=None):
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"""commit all attributes unconditionally.
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This is used after a flush() or a full load/refresh
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to remove all pending state from the instance.
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- all attributes are marked as "committed"
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- the "strong dirty reference" is removed
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- the "modified" flag is set to False
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- any "expired" markers/callables for attributes loaded are removed.
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Attributes marked as "expired" can potentially remain
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"expired" after this step if a value was not populated in state.dict.
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"""
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self._commit_all_states([(self, dict_)], instance_dict)
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@classmethod
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def _commit_all_states(self, iter, instance_dict=None):
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"""Mass version of commit_all()."""
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for state, dict_ in iter:
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state.committed_state.clear()
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InstanceState._pending_mutations._reset(state)
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callables = state.callables
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for key in list(callables):
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if key in dict_ and callables[key] is state:
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del callables[key]
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if instance_dict and state.modified:
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instance_dict._modified.discard(state)
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state.modified = state.expired = False
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state._strong_obj = None
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class AttributeState(object):
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"""Provide an inspection interface corresponding
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to a particular attribute on a particular mapped object.
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The :class:`.AttributeState` object is accessed
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via the :attr:`.InstanceState.attrs` collection
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of a particular :class:`.InstanceState`::
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from sqlalchemy import inspect
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insp = inspect(some_mapped_object)
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attr_state = insp.attrs.some_attribute
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"""
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def __init__(self, state, key):
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self.state = state
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self.key = key
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@property
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def loaded_value(self):
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"""The current value of this attribute as loaded from the database.
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If the value has not been loaded, or is otherwise not present
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in the object's dictionary, returns NO_VALUE.
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"""
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return self.state.dict.get(self.key, NO_VALUE)
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@property
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def value(self):
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"""Return the value of this attribute.
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This operation is equivalent to accessing the object's
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attribute directly or via ``getattr()``, and will fire
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off any pending loader callables if needed.
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"""
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return self.state.manager[self.key].__get__(
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self.state.obj(), self.state.class_)
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@property
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def history(self):
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"""Return the current pre-flush change history for
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this attribute, via the :class:`.History` interface.
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This method will **not** emit loader callables if the value of the
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attribute is unloaded.
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.. seealso::
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:meth:`.AttributeState.load_history` - retrieve history
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using loader callables if the value is not locally present.
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:func:`.attributes.get_history` - underlying function
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"""
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return self.state.get_history(self.key,
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PASSIVE_NO_INITIALIZE)
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def load_history(self):
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"""Return the current pre-flush change history for
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this attribute, via the :class:`.History` interface.
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This method **will** emit loader callables if the value of the
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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)
|