JezK
Edit File: attributes.py
# orm/attributes.py # Copyright (C) 2005-2023 the SQLAlchemy authors and contributors # <see AUTHORS file> # # This module is part of SQLAlchemy and is released under # the MIT License: https://www.opensource.org/licenses/mit-license.php """Defines instrumentation for class attributes and their interaction with instances. This module is usually not directly visible to user applications, but defines a large part of the ORM's interactivity. """ import operator from . import collections from . import exc as orm_exc from . import interfaces from .base import ATTR_EMPTY from .base import ATTR_WAS_SET from .base import CALLABLES_OK from .base import DEFERRED_HISTORY_LOAD from .base import INIT_OK from .base import instance_dict from .base import instance_state from .base import instance_str from .base import LOAD_AGAINST_COMMITTED from .base import manager_of_class from .base import NEVER_SET # noqa from .base import NO_AUTOFLUSH from .base import NO_CHANGE # noqa from .base import NO_RAISE from .base import NO_VALUE from .base import NON_PERSISTENT_OK # noqa from .base import PASSIVE_CLASS_MISMATCH # noqa from .base import PASSIVE_NO_FETCH from .base import PASSIVE_NO_FETCH_RELATED # noqa from .base import PASSIVE_NO_INITIALIZE from .base import PASSIVE_NO_RESULT from .base import PASSIVE_OFF from .base import PASSIVE_ONLY_PERSISTENT from .base import PASSIVE_RETURN_NO_VALUE from .base import RELATED_OBJECT_OK # noqa from .base import SQL_OK # noqa from .base import state_str from .. import event from .. import exc from .. import inspection from .. import util from ..sql import base as sql_base from ..sql import roles from ..sql import traversals from ..sql import visitors class NoKey(str): pass NO_KEY = NoKey("no name") @inspection._self_inspects class QueryableAttribute( interfaces._MappedAttribute, interfaces.InspectionAttr, interfaces.PropComparator, traversals.HasCopyInternals, roles.JoinTargetRole, roles.OnClauseRole, sql_base.Immutable, sql_base.MemoizedHasCacheKey, ): """Base class for :term:`descriptor` objects that intercept attribute events on behalf of a :class:`.MapperProperty` object. The actual :class:`.MapperProperty` is accessible via the :attr:`.QueryableAttribute.property` attribute. .. seealso:: :class:`.InstrumentedAttribute` :class:`.MapperProperty` :attr:`_orm.Mapper.all_orm_descriptors` :attr:`_orm.Mapper.attrs` """ is_attribute = True # PropComparator has a __visit_name__ to participate within # traversals. Disambiguate the attribute vs. a comparator. __visit_name__ = "orm_instrumented_attribute" def __init__( self, class_, key, parententity, impl=None, comparator=None, of_type=None, extra_criteria=(), ): self.class_ = class_ self.key = key self._parententity = parententity self.impl = impl self.comparator = comparator self._of_type = of_type self._extra_criteria = extra_criteria manager = manager_of_class(class_) # manager is None in the case of AliasedClass if manager: # propagate existing event listeners from # immediate superclass for base in manager._bases: if key in base: self.dispatch._update(base[key].dispatch) if base[key].dispatch._active_history: self.dispatch._active_history = True _cache_key_traversal = [ ("key", visitors.ExtendedInternalTraversal.dp_string), ("_parententity", visitors.ExtendedInternalTraversal.dp_multi), ("_of_type", visitors.ExtendedInternalTraversal.dp_multi), ("_extra_criteria", visitors.InternalTraversal.dp_clauseelement_list), ] def __reduce__(self): # this method is only used in terms of the # sqlalchemy.ext.serializer extension return ( _queryable_attribute_unreduce, ( self.key, self._parententity.mapper.class_, self._parententity, self._parententity.entity, ), ) @util.memoized_property def _supports_population(self): return self.impl.supports_population @property def _impl_uses_objects(self): return self.impl.uses_objects def get_history(self, instance, passive=PASSIVE_OFF): return self.impl.get_history( instance_state(instance), instance_dict(instance), passive ) @util.memoized_property def info(self): """Return the 'info' dictionary for the underlying SQL element. The behavior here is as follows: * If the attribute is a column-mapped property, i.e. :class:`.ColumnProperty`, which is mapped directly to a schema-level :class:`_schema.Column` object, this attribute will return the :attr:`.SchemaItem.info` dictionary associated with the core-level :class:`_schema.Column` object. * If the attribute is a :class:`.ColumnProperty` but is mapped to any other kind of SQL expression other than a :class:`_schema.Column`, the attribute will refer to the :attr:`.MapperProperty.info` dictionary associated directly with the :class:`.ColumnProperty`, assuming the SQL expression itself does not have its own ``.info`` attribute (which should be the case, unless a user-defined SQL construct has defined one). * If the attribute refers to any other kind of :class:`.MapperProperty`, including :class:`.RelationshipProperty`, the attribute will refer to the :attr:`.MapperProperty.info` dictionary associated with that :class:`.MapperProperty`. * To access the :attr:`.MapperProperty.info` dictionary of the :class:`.MapperProperty` unconditionally, including for a :class:`.ColumnProperty` that's associated directly with a :class:`_schema.Column`, the attribute can be referred to using :attr:`.QueryableAttribute.property` attribute, as ``MyClass.someattribute.property.info``. .. seealso:: :attr:`.SchemaItem.info` :attr:`.MapperProperty.info` """ return self.comparator.info @util.memoized_property def parent(self): """Return an inspection instance representing the parent. This will be either an instance of :class:`_orm.Mapper` or :class:`.AliasedInsp`, depending upon the nature of the parent entity which this attribute is associated with. """ return inspection.inspect(self._parententity) @util.memoized_property def expression(self): """The SQL expression object represented by this :class:`.QueryableAttribute`. This will typically be an instance of a :class:`_sql.ColumnElement` subclass representing a column expression. """ if self.key is NO_KEY: annotations = {"entity_namespace": self._entity_namespace} else: annotations = { "proxy_key": self.key, "proxy_owner": self._parententity, "entity_namespace": self._entity_namespace, } ce = self.comparator.__clause_element__() try: anno = ce._annotate except AttributeError as ae: util.raise_( exc.InvalidRequestError( 'When interpreting attribute "%s" as a SQL expression, ' "expected __clause_element__() to return " "a ClauseElement object, got: %r" % (self, ce) ), from_=ae, ) else: return anno(annotations) @property def _entity_namespace(self): return self._parententity @property def _annotations(self): return self.__clause_element__()._annotations def __clause_element__(self): return self.expression @property def _from_objects(self): return self.expression._from_objects def _bulk_update_tuples(self, value): """Return setter tuples for a bulk UPDATE.""" return self.comparator._bulk_update_tuples(value) def adapt_to_entity(self, adapt_to_entity): assert not self._of_type return self.__class__( adapt_to_entity.entity, self.key, impl=self.impl, comparator=self.comparator.adapt_to_entity(adapt_to_entity), parententity=adapt_to_entity, ) def of_type(self, entity): return QueryableAttribute( self.class_, self.key, self._parententity, impl=self.impl, comparator=self.comparator.of_type(entity), of_type=inspection.inspect(entity), extra_criteria=self._extra_criteria, ) def and_(self, *other): return QueryableAttribute( self.class_, self.key, self._parententity, impl=self.impl, comparator=self.comparator.and_(*other), of_type=self._of_type, extra_criteria=self._extra_criteria + other, ) def _clone(self, **kw): return QueryableAttribute( self.class_, self.key, self._parententity, impl=self.impl, comparator=self.comparator, of_type=self._of_type, extra_criteria=self._extra_criteria, ) def label(self, name): return self.__clause_element__().label(name) def operate(self, op, *other, **kwargs): return op(self.comparator, *other, **kwargs) def reverse_operate(self, op, other, **kwargs): return op(other, self.comparator, **kwargs) def hasparent(self, state, optimistic=False): return self.impl.hasparent(state, optimistic=optimistic) is not False def __getattr__(self, key): try: return getattr(self.comparator, key) except AttributeError as err: util.raise_( AttributeError( "Neither %r object nor %r object associated with %s " "has an attribute %r" % ( type(self).__name__, type(self.comparator).__name__, self, key, ) ), replace_context=err, ) def __str__(self): return "%s.%s" % (self.class_.__name__, self.key) @util.memoized_property def property(self): """Return the :class:`.MapperProperty` associated with this :class:`.QueryableAttribute`. Return values here will commonly be instances of :class:`.ColumnProperty` or :class:`.RelationshipProperty`. """ return self.comparator.property def _queryable_attribute_unreduce(key, mapped_class, parententity, entity): # this method is only used in terms of the # sqlalchemy.ext.serializer extension if parententity.is_aliased_class: return entity._get_from_serialized(key, mapped_class, parententity) else: return getattr(entity, key) if util.py3k: from typing import TypeVar, Generic _T = TypeVar("_T") _Generic_T = Generic[_T] else: _Generic_T = type("_Generic_T", (), {}) class Mapped(QueryableAttribute, _Generic_T): """Represent an ORM mapped :term:`descriptor` attribute for typing purposes. This class represents the complete descriptor interface for any class attribute that will have been :term:`instrumented` by the ORM :class:`_orm.Mapper` class. When used with typing stubs, it is the final type that would be used by a type checker such as mypy to provide the full behavioral contract for the attribute. .. tip:: The :class:`_orm.Mapped` class represents attributes that are handled directly by the :class:`_orm.Mapper` class. It does not include other Python descriptor classes that are provided as extensions, including :ref:`hybrids_toplevel` and the :ref:`associationproxy_toplevel`. While these systems still make use of ORM-specific superclasses and structures, they are not :term:`instrumented` by the :class:`_orm.Mapper` and instead provide their own functionality when they are accessed on a class. When using the :ref:`SQLAlchemy Mypy plugin <mypy_toplevel>`, the :class:`_orm.Mapped` construct is used in typing annotations to indicate to the plugin those attributes that are expected to be mapped; the plugin also applies :class:`_orm.Mapped` as an annotation automatically when it scans through declarative mappings in :ref:`orm_declarative_table` style. For more indirect mapping styles such as :ref:`imperative table <orm_imperative_table_configuration>` it is typically applied explicitly to class level attributes that expect to be mapped based on a given :class:`_schema.Table` configuration. :class:`_orm.Mapped` is defined in the `sqlalchemy2-stubs <https://pypi.org/project/sqlalchemy2-stubs>`_ project as a :pep:`484` generic class which may subscribe to any arbitrary Python type, which represents the Python type handled by the attribute:: class MyMappedClass(Base): __table_ = Table( "some_table", Base.metadata, Column("id", Integer, primary_key=True), Column("data", String(50)), Column("created_at", DateTime) ) id : Mapped[int] data: Mapped[str] created_at: Mapped[datetime] For complete background on how to use :class:`_orm.Mapped` with pep-484 tools like Mypy, see the link below for background on SQLAlchemy's Mypy plugin. .. versionadded:: 1.4 .. seealso:: :ref:`mypy_toplevel` - complete background on Mypy integration """ def __get__(self, instance, owner): raise NotImplementedError() def __set__(self, instance, value): raise NotImplementedError() def __delete__(self, instance): raise NotImplementedError() class InstrumentedAttribute(Mapped): """Class bound instrumented attribute which adds basic :term:`descriptor` methods. See :class:`.QueryableAttribute` for a description of most features. """ inherit_cache = True def __set__(self, instance, value): self.impl.set( instance_state(instance), instance_dict(instance), value, None ) def __delete__(self, instance): self.impl.delete(instance_state(instance), instance_dict(instance)) def __get__(self, instance, owner): if instance is None: return self dict_ = instance_dict(instance) if self._supports_population and self.key in dict_: return dict_[self.key] else: try: state = instance_state(instance) except AttributeError as err: util.raise_( orm_exc.UnmappedInstanceError(instance), replace_context=err, ) return self.impl.get(state, dict_) HasEntityNamespace = util.namedtuple( "HasEntityNamespace", ["entity_namespace"] ) HasEntityNamespace.is_mapper = HasEntityNamespace.is_aliased_class = False def create_proxied_attribute(descriptor): """Create an QueryableAttribute / user descriptor hybrid. Returns a new QueryableAttribute type that delegates descriptor behavior and getattr() to the given descriptor. """ # TODO: can move this to descriptor_props if the need for this # function is removed from ext/hybrid.py class Proxy(QueryableAttribute): """Presents the :class:`.QueryableAttribute` interface as a proxy on top of a Python descriptor / :class:`.PropComparator` combination. """ _extra_criteria = () def __init__( self, class_, key, descriptor, comparator, adapt_to_entity=None, doc=None, original_property=None, ): self.class_ = class_ self.key = key self.descriptor = descriptor self.original_property = original_property self._comparator = comparator self._adapt_to_entity = adapt_to_entity self.__doc__ = doc _is_internal_proxy = True _cache_key_traversal = [ ("key", visitors.ExtendedInternalTraversal.dp_string), ("_parententity", visitors.ExtendedInternalTraversal.dp_multi), ] @property def _impl_uses_objects(self): return ( self.original_property is not None and getattr(self.class_, self.key).impl.uses_objects ) @property def _parententity(self): return inspection.inspect(self.class_, raiseerr=False) @property def _entity_namespace(self): if hasattr(self._comparator, "_parententity"): return self._comparator._parententity else: # used by hybrid attributes which try to remain # agnostic of any ORM concepts like mappers return HasEntityNamespace(self.class_) @property def property(self): return self.comparator.property @util.memoized_property def comparator(self): if callable(self._comparator): self._comparator = self._comparator() if self._adapt_to_entity: self._comparator = self._comparator.adapt_to_entity( self._adapt_to_entity ) return self._comparator def adapt_to_entity(self, adapt_to_entity): return self.__class__( adapt_to_entity.entity, self.key, self.descriptor, self._comparator, adapt_to_entity, ) def _clone(self, **kw): return self.__class__( self.class_, self.key, self.descriptor, self._comparator, adapt_to_entity=self._adapt_to_entity, original_property=self.original_property, ) def __get__(self, instance, owner): retval = self.descriptor.__get__(instance, owner) # detect if this is a plain Python @property, which just returns # itself for class level access. If so, then return us. # Otherwise, return the object returned by the descriptor. if retval is self.descriptor and instance is None: return self else: return retval def __str__(self): return "%s.%s" % (self.class_.__name__, self.key) def __getattr__(self, attribute): """Delegate __getattr__ to the original descriptor and/or comparator.""" try: return getattr(descriptor, attribute) except AttributeError as err: if attribute == "comparator": util.raise_( AttributeError("comparator"), replace_context=err ) try: # comparator itself might be unreachable comparator = self.comparator except AttributeError as err2: util.raise_( AttributeError( "Neither %r object nor unconfigured comparator " "object associated with %s has an attribute %r" % (type(descriptor).__name__, self, attribute) ), replace_context=err2, ) else: try: return getattr(comparator, attribute) except AttributeError as err3: util.raise_( AttributeError( "Neither %r object nor %r object " "associated with %s has an attribute %r" % ( type(descriptor).__name__, type(comparator).__name__, self, attribute, ) ), replace_context=err3, ) Proxy.__name__ = type(descriptor).__name__ + "Proxy" util.monkeypatch_proxied_specials( Proxy, type(descriptor), name="descriptor", from_instance=descriptor ) return Proxy OP_REMOVE = util.symbol("REMOVE") OP_APPEND = util.symbol("APPEND") OP_REPLACE = util.symbol("REPLACE") OP_BULK_REPLACE = util.symbol("BULK_REPLACE") OP_MODIFIED = util.symbol("MODIFIED") class AttributeEvent(object): """A token propagated throughout the course of a chain of attribute events. Serves as an indicator of the source of the event and also provides a means of controlling propagation across a chain of attribute operations. The :class:`.Event` object is sent as the ``initiator`` argument when dealing with events such as :meth:`.AttributeEvents.append`, :meth:`.AttributeEvents.set`, and :meth:`.AttributeEvents.remove`. The :class:`.Event` object is currently interpreted by the backref event handlers, and is used to control the propagation of operations across two mutually-dependent attributes. .. versionadded:: 0.9.0 :attribute impl: The :class:`.AttributeImpl` which is the current event initiator. :attribute op: The symbol :attr:`.OP_APPEND`, :attr:`.OP_REMOVE`, :attr:`.OP_REPLACE`, or :attr:`.OP_BULK_REPLACE`, indicating the source operation. """ __slots__ = "impl", "op", "parent_token" def __init__(self, attribute_impl, op): self.impl = attribute_impl self.op = op self.parent_token = self.impl.parent_token def __eq__(self, other): return ( isinstance(other, AttributeEvent) and other.impl is self.impl and other.op == self.op ) @property def key(self): return self.impl.key def hasparent(self, state): return self.impl.hasparent(state) Event = AttributeEvent class AttributeImpl(object): """internal implementation for instrumented attributes.""" def __init__( self, class_, key, callable_, dispatch, trackparent=False, compare_function=None, active_history=False, parent_token=None, load_on_unexpire=True, send_modified_events=True, accepts_scalar_loader=None, **kwargs ): r"""Construct an AttributeImpl. :param \class_: associated class :param key: string name of the attribute :param \callable_: optional function which generates a callable based on a parent instance, which produces the "default" values for a scalar or collection attribute when it's first accessed, if not present already. :param trackparent: if True, attempt to track if an instance has a parent attached to it via this attribute. :param compare_function: a function that compares two values which are normally assignable to this attribute. :param active_history: indicates that get_history() should always return the "old" value, even if it means executing a lazy callable upon attribute change. :param parent_token: Usually references the MapperProperty, used as a key for the hasparent() function to identify an "owning" attribute. Allows multiple AttributeImpls to all match a single owner attribute. :param load_on_unexpire: if False, don't include this attribute in a load-on-expired operation, i.e. the "expired_attribute_loader" process. The attribute can still be in the "expired" list and be considered to be "expired". Previously, this flag was called "expire_missing" and is only used by a deferred column attribute. :param send_modified_events: if False, the InstanceState._modified_event method will have no effect; this means the attribute will never show up as changed in a history entry. """ self.class_ = class_ self.key = key self.callable_ = callable_ self.dispatch = dispatch self.trackparent = trackparent self.parent_token = parent_token or self self.send_modified_events = send_modified_events if compare_function is None: self.is_equal = operator.eq else: self.is_equal = compare_function if accepts_scalar_loader is not None: self.accepts_scalar_loader = accepts_scalar_loader else: self.accepts_scalar_loader = self.default_accepts_scalar_loader _deferred_history = kwargs.pop("_deferred_history", False) self._deferred_history = _deferred_history if active_history: self.dispatch._active_history = True self.load_on_unexpire = load_on_unexpire self._modified_token = Event(self, OP_MODIFIED) __slots__ = ( "class_", "key", "callable_", "dispatch", "trackparent", "parent_token", "send_modified_events", "is_equal", "load_on_unexpire", "_modified_token", "accepts_scalar_loader", "_deferred_history", ) def __str__(self): return "%s.%s" % (self.class_.__name__, self.key) def _get_active_history(self): """Backwards compat for impl.active_history""" return self.dispatch._active_history def _set_active_history(self, value): self.dispatch._active_history = value active_history = property(_get_active_history, _set_active_history) def hasparent(self, state, optimistic=False): """Return the boolean value of a `hasparent` flag attached to the given state. The `optimistic` flag determines what the default return value should be if no `hasparent` flag can be located. As this function is used to determine if an instance is an *orphan*, instances that were loaded from storage should be assumed to not be orphans, until a True/False value for this flag is set. An instance attribute that is loaded by a callable function will also not have a `hasparent` flag. """ msg = "This AttributeImpl is not configured to track parents." assert self.trackparent, msg return ( state.parents.get(id(self.parent_token), optimistic) is not False ) def sethasparent(self, state, parent_state, value): """Set a boolean flag on the given item corresponding to whether or not it is attached to a parent object via the attribute represented by this ``InstrumentedAttribute``. """ msg = "This AttributeImpl is not configured to track parents." assert self.trackparent, msg id_ = id(self.parent_token) if value: state.parents[id_] = parent_state else: if id_ in state.parents: last_parent = state.parents[id_] if ( last_parent is not False and last_parent.key != parent_state.key ): if last_parent.obj() is None: raise orm_exc.StaleDataError( "Removing state %s from parent " "state %s along attribute '%s', " "but the parent record " "has gone stale, can't be sure this " "is the most recent parent." % ( state_str(state), state_str(parent_state), self.key, ) ) return state.parents[id_] = False def get_history(self, state, dict_, passive=PASSIVE_OFF): raise NotImplementedError() def get_all_pending(self, state, dict_, passive=PASSIVE_NO_INITIALIZE): """Return a list of tuples of (state, obj) for all objects in this attribute's current state + history. Only applies to object-based attributes. This is an inlining of existing functionality which roughly corresponds to: get_state_history( state, key, passive=PASSIVE_NO_INITIALIZE).sum() """ raise NotImplementedError() def _default_value(self, state, dict_): """Produce an empty value for an uninitialized scalar attribute.""" assert self.key not in dict_, ( "_default_value should only be invoked for an " "uninitialized or expired attribute" ) value = None for fn in self.dispatch.init_scalar: ret = fn(state, value, dict_) if ret is not ATTR_EMPTY: value = ret return value def get(self, state, dict_, passive=PASSIVE_OFF): """Retrieve a value from the given object. If a callable is assembled on this object's attribute, and passive is False, the callable will be executed and the resulting value will be set as the new value for this attribute. """ if self.key in dict_: return dict_[self.key] else: # if history present, don't load key = self.key if ( key not in state.committed_state or state.committed_state[key] is NO_VALUE ): if not passive & CALLABLES_OK: return PASSIVE_NO_RESULT value = self._fire_loader_callables(state, key, passive) if value is PASSIVE_NO_RESULT or value is NO_VALUE: return value elif value is ATTR_WAS_SET: try: return dict_[key] except KeyError as err: # TODO: no test coverage here. util.raise_( KeyError( "Deferred loader for attribute " "%r failed to populate " "correctly" % key ), replace_context=err, ) elif value is not ATTR_EMPTY: return self.set_committed_value(state, dict_, value) if not passive & INIT_OK: return NO_VALUE else: return self._default_value(state, dict_) def _fire_loader_callables(self, state, key, passive): if ( self.accepts_scalar_loader and self.load_on_unexpire and key in state.expired_attributes ): return state._load_expired(state, passive) elif key in state.callables: callable_ = state.callables[key] return callable_(state, passive) elif self.callable_: return self.callable_(state, passive) else: return ATTR_EMPTY def append(self, state, dict_, value, initiator, passive=PASSIVE_OFF): self.set(state, dict_, value, initiator, passive=passive) def remove(self, state, dict_, value, initiator, passive=PASSIVE_OFF): self.set( state, dict_, None, initiator, passive=passive, check_old=value ) def pop(self, state, dict_, value, initiator, passive=PASSIVE_OFF): self.set( state, dict_, None, initiator, passive=passive, check_old=value, pop=True, ) def set( self, state, dict_, value, initiator, passive=PASSIVE_OFF, check_old=None, pop=False, ): raise NotImplementedError() def get_committed_value(self, state, dict_, passive=PASSIVE_OFF): """return the unchanged value of this attribute""" if self.key in state.committed_state: value = state.committed_state[self.key] if value is NO_VALUE: return None else: return value else: return self.get(state, dict_, passive=passive) def set_committed_value(self, state, dict_, value): """set an attribute value on the given instance and 'commit' it.""" dict_[self.key] = value state._commit(dict_, [self.key]) return value class ScalarAttributeImpl(AttributeImpl): """represents a scalar value-holding InstrumentedAttribute.""" default_accepts_scalar_loader = True uses_objects = False supports_population = True collection = False dynamic = False __slots__ = "_replace_token", "_append_token", "_remove_token" def __init__(self, *arg, **kw): super(ScalarAttributeImpl, self).__init__(*arg, **kw) self._replace_token = self._append_token = Event(self, OP_REPLACE) self._remove_token = Event(self, OP_REMOVE) def delete(self, state, dict_): if self.dispatch._active_history: old = self.get(state, dict_, PASSIVE_RETURN_NO_VALUE) else: old = dict_.get(self.key, NO_VALUE) if self.dispatch.remove: self.fire_remove_event(state, dict_, old, self._remove_token) state._modified_event(dict_, self, old) existing = dict_.pop(self.key, NO_VALUE) if ( existing is NO_VALUE and old is NO_VALUE and not state.expired and self.key not in state.expired_attributes ): raise AttributeError("%s object does not have a value" % self) def get_history(self, state, dict_, passive=PASSIVE_OFF): if self.key in dict_: return History.from_scalar_attribute(self, state, dict_[self.key]) elif self.key in state.committed_state: return History.from_scalar_attribute(self, state, NO_VALUE) else: if passive & INIT_OK: passive ^= INIT_OK current = self.get(state, dict_, passive=passive) if current is PASSIVE_NO_RESULT: return HISTORY_BLANK else: return History.from_scalar_attribute(self, state, current) def set( self, state, dict_, value, initiator, passive=PASSIVE_OFF, check_old=None, pop=False, ): if self.dispatch._active_history: old = self.get(state, dict_, PASSIVE_RETURN_NO_VALUE) else: old = dict_.get(self.key, NO_VALUE) if self.dispatch.set: value = self.fire_replace_event( state, dict_, value, old, initiator ) state._modified_event(dict_, self, old) dict_[self.key] = value def fire_replace_event(self, state, dict_, value, previous, initiator): for fn in self.dispatch.set: value = fn( state, value, previous, initiator or self._replace_token ) return value def fire_remove_event(self, state, dict_, value, initiator): for fn in self.dispatch.remove: fn(state, value, initiator or self._remove_token) @property def type(self): self.property.columns[0].type class ScalarObjectAttributeImpl(ScalarAttributeImpl): """represents a scalar-holding InstrumentedAttribute, where the target object is also instrumented. Adds events to delete/set operations. """ default_accepts_scalar_loader = False uses_objects = True supports_population = True collection = False __slots__ = () def delete(self, state, dict_): if self.dispatch._active_history: old = self.get( state, dict_, passive=PASSIVE_ONLY_PERSISTENT | NO_AUTOFLUSH | LOAD_AGAINST_COMMITTED, ) else: old = self.get( state, dict_, passive=PASSIVE_NO_FETCH ^ INIT_OK | LOAD_AGAINST_COMMITTED | NO_RAISE, ) self.fire_remove_event(state, dict_, old, self._remove_token) existing = dict_.pop(self.key, NO_VALUE) # if the attribute is expired, we currently have no way to tell # that an object-attribute was expired vs. not loaded. So # for this test, we look to see if the object has a DB identity. if ( existing is NO_VALUE and old is not PASSIVE_NO_RESULT and state.key is None ): raise AttributeError("%s object does not have a value" % self) def get_history(self, state, dict_, passive=PASSIVE_OFF): if self.key in dict_: current = dict_[self.key] else: if passive & INIT_OK: passive ^= INIT_OK current = self.get(state, dict_, passive=passive) if current is PASSIVE_NO_RESULT: return HISTORY_BLANK if not self._deferred_history: return History.from_object_attribute(self, state, current) else: original = state.committed_state.get(self.key, _NO_HISTORY) if original is PASSIVE_NO_RESULT: loader_passive = passive | ( PASSIVE_ONLY_PERSISTENT | NO_AUTOFLUSH | LOAD_AGAINST_COMMITTED | NO_RAISE | DEFERRED_HISTORY_LOAD ) original = self._fire_loader_callables( state, self.key, loader_passive ) return History.from_object_attribute( self, state, current, original=original ) def get_all_pending(self, state, dict_, passive=PASSIVE_NO_INITIALIZE): if self.key in dict_: current = dict_[self.key] elif passive & CALLABLES_OK: current = self.get(state, dict_, passive=passive) else: return [] # can't use __hash__(), can't use __eq__() here if ( current is not None and current is not PASSIVE_NO_RESULT and current is not NO_VALUE ): ret = [(instance_state(current), current)] else: ret = [(None, None)] if self.key in state.committed_state: original = state.committed_state[self.key] if ( original is not None and original is not PASSIVE_NO_RESULT and original is not NO_VALUE and original is not current ): ret.append((instance_state(original), original)) return ret def set( self, state, dict_, value, initiator, passive=PASSIVE_OFF, check_old=None, pop=False, ): """Set a value on the given InstanceState.""" if self.dispatch._active_history: old = self.get( state, dict_, passive=PASSIVE_ONLY_PERSISTENT | NO_AUTOFLUSH | LOAD_AGAINST_COMMITTED, ) else: old = self.get( state, dict_, passive=PASSIVE_NO_FETCH ^ INIT_OK | LOAD_AGAINST_COMMITTED | NO_RAISE, ) if ( check_old is not None and old is not PASSIVE_NO_RESULT and check_old is not old ): if pop: return else: raise ValueError( "Object %s not associated with %s on attribute '%s'" % (instance_str(check_old), state_str(state), self.key) ) value = self.fire_replace_event(state, dict_, value, old, initiator) dict_[self.key] = value def fire_remove_event(self, state, dict_, value, initiator): if self.trackparent and value not in ( None, PASSIVE_NO_RESULT, NO_VALUE, ): self.sethasparent(instance_state(value), state, False) for fn in self.dispatch.remove: fn(state, value, initiator or self._remove_token) state._modified_event(dict_, self, value) def fire_replace_event(self, state, dict_, value, previous, initiator): if self.trackparent: if previous is not value and previous not in ( None, PASSIVE_NO_RESULT, NO_VALUE, ): self.sethasparent(instance_state(previous), state, False) for fn in self.dispatch.set: value = fn( state, value, previous, initiator or self._replace_token ) state._modified_event(dict_, self, previous) if self.trackparent: if value is not None: self.sethasparent(instance_state(value), state, True) return value class CollectionAttributeImpl(AttributeImpl): """A collection-holding attribute that instruments changes in membership. Only handles collections of instrumented objects. InstrumentedCollectionAttribute holds an arbitrary, user-specified container object (defaulting to a list) and brokers access to the CollectionAdapter, a "view" onto that object that presents consistent bag semantics to the orm layer independent of the user data implementation. """ default_accepts_scalar_loader = False uses_objects = True supports_population = True collection = True dynamic = False __slots__ = ( "copy", "collection_factory", "_append_token", "_remove_token", "_bulk_replace_token", "_duck_typed_as", ) def __init__( self, class_, key, callable_, dispatch, typecallable=None, trackparent=False, copy_function=None, compare_function=None, **kwargs ): super(CollectionAttributeImpl, self).__init__( class_, key, callable_, dispatch, trackparent=trackparent, compare_function=compare_function, **kwargs ) if copy_function is None: copy_function = self.__copy self.copy = copy_function self.collection_factory = typecallable self._append_token = Event(self, OP_APPEND) self._remove_token = Event(self, OP_REMOVE) self._bulk_replace_token = Event(self, OP_BULK_REPLACE) self._duck_typed_as = util.duck_type_collection( self.collection_factory() ) if getattr(self.collection_factory, "_sa_linker", None): @event.listens_for(self, "init_collection") def link(target, collection, collection_adapter): collection._sa_linker(collection_adapter) @event.listens_for(self, "dispose_collection") def unlink(target, collection, collection_adapter): collection._sa_linker(None) def __copy(self, item): return [y for y in collections.collection_adapter(item)] def get_history(self, state, dict_, passive=PASSIVE_OFF): current = self.get(state, dict_, passive=passive) if current is PASSIVE_NO_RESULT: return HISTORY_BLANK else: return History.from_collection(self, state, current) def get_all_pending(self, state, dict_, passive=PASSIVE_NO_INITIALIZE): # NOTE: passive is ignored here at the moment if self.key not in dict_: return [] current = dict_[self.key] current = getattr(current, "_sa_adapter") if self.key in state.committed_state: original = state.committed_state[self.key] if original is not NO_VALUE: current_states = [ ((c is not None) and instance_state(c) or None, c) for c in current ] original_states = [ ((c is not None) and instance_state(c) or None, c) for c in original ] current_set = dict(current_states) original_set = dict(original_states) return ( [ (s, o) for s, o in current_states if s not in original_set ] + [(s, o) for s, o in current_states if s in original_set] + [ (s, o) for s, o in original_states if s not in current_set ] ) return [(instance_state(o), o) for o in current] def fire_append_event(self, state, dict_, value, initiator): for fn in self.dispatch.append: value = fn(state, value, initiator or self._append_token) state._modified_event(dict_, self, NO_VALUE, True) if self.trackparent and value is not None: self.sethasparent(instance_state(value), state, True) return value def fire_append_wo_mutation_event(self, state, dict_, value, initiator): for fn in self.dispatch.append_wo_mutation: value = fn(state, value, initiator or self._append_token) return value def fire_pre_remove_event(self, state, dict_, initiator): """A special event used for pop() operations. The "remove" event needs to have the item to be removed passed to it, which in the case of pop from a set, we don't have a way to access the item before the operation. the event is used for all pop() operations (even though set.pop is the one where it is really needed). """ state._modified_event(dict_, self, NO_VALUE, True) def fire_remove_event(self, state, dict_, value, initiator): if self.trackparent and value is not None: self.sethasparent(instance_state(value), state, False) for fn in self.dispatch.remove: fn(state, value, initiator or self._remove_token) state._modified_event(dict_, self, NO_VALUE, True) def delete(self, state, dict_): if self.key not in dict_: return state._modified_event(dict_, self, NO_VALUE, True) collection = self.get_collection(state, state.dict) collection.clear_with_event() # key is always present because we checked above. e.g. # del is a no-op if collection not present. del dict_[self.key] def _default_value(self, state, dict_): """Produce an empty collection for an un-initialized attribute""" assert self.key not in dict_, ( "_default_value should only be invoked for an " "uninitialized or expired attribute" ) if self.key in state._empty_collections: return state._empty_collections[self.key] adapter, user_data = self._initialize_collection(state) adapter._set_empty(user_data) return user_data def _initialize_collection(self, state): adapter, collection = state.manager.initialize_collection( self.key, state, self.collection_factory ) self.dispatch.init_collection(state, collection, adapter) return adapter, collection def append(self, state, dict_, value, initiator, passive=PASSIVE_OFF): collection = self.get_collection(state, dict_, passive=passive) if collection is PASSIVE_NO_RESULT: value = self.fire_append_event(state, dict_, value, initiator) assert ( self.key not in dict_ ), "Collection was loaded during event handling." state._get_pending_mutation(self.key).append(value) else: collection.append_with_event(value, initiator) def remove(self, state, dict_, value, initiator, passive=PASSIVE_OFF): collection = self.get_collection(state, state.dict, passive=passive) if collection is PASSIVE_NO_RESULT: self.fire_remove_event(state, dict_, value, initiator) assert ( self.key not in dict_ ), "Collection was loaded during event handling." state._get_pending_mutation(self.key).remove(value) else: collection.remove_with_event(value, initiator) def pop(self, state, dict_, value, initiator, passive=PASSIVE_OFF): try: # TODO: better solution here would be to add # a "popper" role to collections.py to complement # "remover". self.remove(state, dict_, value, initiator, passive=passive) except (ValueError, KeyError, IndexError): pass def set( self, state, dict_, value, initiator=None, passive=PASSIVE_OFF, check_old=None, pop=False, _adapt=True, ): iterable = orig_iterable = value # pulling a new collection first so that an adaptation exception does # not trigger a lazy load of the old collection. new_collection, user_data = self._initialize_collection(state) if _adapt: if new_collection._converter is not None: iterable = new_collection._converter(iterable) else: setting_type = util.duck_type_collection(iterable) receiving_type = self._duck_typed_as if setting_type is not receiving_type: given = ( iterable is None and "None" or iterable.__class__.__name__ ) wanted = self._duck_typed_as.__name__ raise TypeError( "Incompatible collection type: %s is not %s-like" % (given, wanted) ) # If the object is an adapted collection, return the (iterable) # adapter. if hasattr(iterable, "_sa_iterator"): iterable = iterable._sa_iterator() elif setting_type is dict: if util.py3k: iterable = iterable.values() else: iterable = getattr( iterable, "itervalues", iterable.values )() else: iterable = iter(iterable) new_values = list(iterable) evt = self._bulk_replace_token self.dispatch.bulk_replace(state, new_values, evt) # propagate NO_RAISE in passive through to the get() for the # existing object (ticket #8862) old = self.get( state, dict_, passive=PASSIVE_ONLY_PERSISTENT ^ (passive & NO_RAISE), ) if old is PASSIVE_NO_RESULT: old = self._default_value(state, dict_) elif old is orig_iterable: # ignore re-assignment of the current collection, as happens # implicitly with in-place operators (foo.collection |= other) return # place a copy of "old" in state.committed_state state._modified_event(dict_, self, old, True) old_collection = old._sa_adapter dict_[self.key] = user_data collections.bulk_replace( new_values, old_collection, new_collection, initiator=evt ) self._dispose_previous_collection(state, old, old_collection, True) def _dispose_previous_collection( self, state, collection, adapter, fire_event ): del collection._sa_adapter # discarding old collection make sure it is not referenced in empty # collections. state._empty_collections.pop(self.key, None) if fire_event: self.dispatch.dispose_collection(state, collection, adapter) def _invalidate_collection(self, collection): adapter = getattr(collection, "_sa_adapter") adapter.invalidated = True def set_committed_value(self, state, dict_, value): """Set an attribute value on the given instance and 'commit' it.""" collection, user_data = self._initialize_collection(state) if value: collection.append_multiple_without_event(value) state.dict[self.key] = user_data state._commit(dict_, [self.key]) if self.key in state._pending_mutations: # pending items exist. issue a modified event, # add/remove new items. state._modified_event(dict_, self, user_data, True) pending = state._pending_mutations.pop(self.key) added = pending.added_items removed = pending.deleted_items for item in added: collection.append_without_event(item) for item in removed: collection.remove_without_event(item) return user_data def get_collection( self, state, dict_, user_data=None, passive=PASSIVE_OFF ): """Retrieve the CollectionAdapter associated with the given state. if user_data is None, retrieves it from the state using normal "get()" rules, which will fire lazy callables or return the "empty" collection value. """ if user_data is None: user_data = self.get(state, dict_, passive=passive) if user_data is PASSIVE_NO_RESULT: return user_data return user_data._sa_adapter def backref_listeners(attribute, key, uselist): """Apply listeners to synchronize a two-way relationship.""" # use easily recognizable names for stack traces. # in the sections marked "tokens to test for a recursive loop", # this is somewhat brittle and very performance-sensitive logic # that is specific to how we might arrive at each event. a marker # that can target us directly to arguments being invoked against # the impl might be simpler, but could interfere with other systems. parent_token = attribute.impl.parent_token parent_impl = attribute.impl def _acceptable_key_err(child_state, initiator, child_impl): raise ValueError( "Bidirectional attribute conflict detected: " 'Passing object %s to attribute "%s" ' 'triggers a modify event on attribute "%s" ' 'via the backref "%s".' % ( state_str(child_state), initiator.parent_token, child_impl.parent_token, attribute.impl.parent_token, ) ) def emit_backref_from_scalar_set_event(state, child, oldchild, initiator): if oldchild is child: return child if ( oldchild is not None and oldchild is not PASSIVE_NO_RESULT and oldchild is not NO_VALUE ): # With lazy=None, there's no guarantee that the full collection is # present when updating via a backref. old_state, old_dict = ( instance_state(oldchild), instance_dict(oldchild), ) impl = old_state.manager[key].impl # tokens to test for a recursive loop. if not impl.collection and not impl.dynamic: check_recursive_token = impl._replace_token else: check_recursive_token = impl._remove_token if initiator is not check_recursive_token: impl.pop( old_state, old_dict, state.obj(), parent_impl._append_token, passive=PASSIVE_NO_FETCH, ) if child is not None: child_state, child_dict = ( instance_state(child), instance_dict(child), ) child_impl = child_state.manager[key].impl if ( initiator.parent_token is not parent_token and initiator.parent_token is not child_impl.parent_token ): _acceptable_key_err(state, initiator, child_impl) # tokens to test for a recursive loop. check_append_token = child_impl._append_token check_bulk_replace_token = ( child_impl._bulk_replace_token if child_impl.collection else None ) if ( initiator is not check_append_token and initiator is not check_bulk_replace_token ): child_impl.append( child_state, child_dict, state.obj(), initiator, passive=PASSIVE_NO_FETCH, ) return child def emit_backref_from_collection_append_event(state, child, initiator): if child is None: return child_state, child_dict = instance_state(child), instance_dict(child) child_impl = child_state.manager[key].impl if ( initiator.parent_token is not parent_token and initiator.parent_token is not child_impl.parent_token ): _acceptable_key_err(state, initiator, child_impl) # tokens to test for a recursive loop. check_append_token = child_impl._append_token check_bulk_replace_token = ( child_impl._bulk_replace_token if child_impl.collection else None ) if ( initiator is not check_append_token and initiator is not check_bulk_replace_token ): child_impl.append( child_state, child_dict, state.obj(), initiator, passive=PASSIVE_NO_FETCH, ) return child def emit_backref_from_collection_remove_event(state, child, initiator): if ( child is not None and child is not PASSIVE_NO_RESULT and child is not NO_VALUE ): child_state, child_dict = ( instance_state(child), instance_dict(child), ) child_impl = child_state.manager[key].impl # tokens to test for a recursive loop. if not child_impl.collection and not child_impl.dynamic: check_remove_token = child_impl._remove_token check_replace_token = child_impl._replace_token check_for_dupes_on_remove = uselist and not parent_impl.dynamic else: check_remove_token = child_impl._remove_token check_replace_token = ( child_impl._bulk_replace_token if child_impl.collection else None ) check_for_dupes_on_remove = False if ( initiator is not check_remove_token and initiator is not check_replace_token ): if not check_for_dupes_on_remove or not util.has_dupes( # when this event is called, the item is usually # present in the list, except for a pop() operation. state.dict[parent_impl.key], child, ): child_impl.pop( child_state, child_dict, state.obj(), initiator, passive=PASSIVE_NO_FETCH, ) if uselist: event.listen( attribute, "append", emit_backref_from_collection_append_event, retval=True, raw=True, ) else: event.listen( attribute, "set", emit_backref_from_scalar_set_event, retval=True, raw=True, ) # TODO: need coverage in test/orm/ of remove event event.listen( attribute, "remove", emit_backref_from_collection_remove_event, retval=True, raw=True, ) _NO_HISTORY = util.symbol("NO_HISTORY") _NO_STATE_SYMBOLS = frozenset([id(PASSIVE_NO_RESULT), id(NO_VALUE)]) class History(util.namedtuple("History", ["added", "unchanged", "deleted"])): """A 3-tuple of added, unchanged and deleted values, representing the changes which have occurred on an instrumented attribute. The easiest way to get a :class:`.History` object for a particular attribute on an object is to use the :func:`_sa.inspect` function:: from sqlalchemy import inspect hist = inspect(myobject).attrs.myattribute.history Each tuple member is an iterable sequence: * ``added`` - the collection of items added to the attribute (the first tuple element). * ``unchanged`` - the collection of items that have not changed on the attribute (the second tuple element). * ``deleted`` - the collection of items that have been removed from the attribute (the third tuple element). """ def __bool__(self): return self != HISTORY_BLANK __nonzero__ = __bool__ def empty(self): """Return True if this :class:`.History` has no changes and no existing, unchanged state. """ return not bool((self.added or self.deleted) or self.unchanged) def sum(self): """Return a collection of added + unchanged + deleted.""" return ( (self.added or []) + (self.unchanged or []) + (self.deleted or []) ) def non_deleted(self): """Return a collection of added + unchanged.""" return (self.added or []) + (self.unchanged or []) def non_added(self): """Return a collection of unchanged + deleted.""" return (self.unchanged or []) + (self.deleted or []) def has_changes(self): """Return True if this :class:`.History` has changes.""" return bool(self.added or self.deleted) def as_state(self): return History( [ (c is not None) and instance_state(c) or None for c in self.added ], [ (c is not None) and instance_state(c) or None for c in self.unchanged ], [ (c is not None) and instance_state(c) or None for c in self.deleted ], ) @classmethod def from_scalar_attribute(cls, attribute, state, current): original = state.committed_state.get(attribute.key, _NO_HISTORY) if original is _NO_HISTORY: if current is NO_VALUE: return cls((), (), ()) else: return cls((), [current], ()) # don't let ClauseElement expressions here trip things up elif ( current is not NO_VALUE and attribute.is_equal(current, original) is True ): return cls((), [current], ()) else: # current convention on native scalars is to not # include information # about missing previous value in "deleted", but # we do include None, which helps in some primary # key situations if id(original) in _NO_STATE_SYMBOLS: deleted = () # indicate a "del" operation occurred when we don't have # the previous value as: ([None], (), ()) if id(current) in _NO_STATE_SYMBOLS: current = None else: deleted = [original] if current is NO_VALUE: return cls((), (), deleted) else: return cls([current], (), deleted) @classmethod def from_object_attribute( cls, attribute, state, current, original=_NO_HISTORY ): if original is _NO_HISTORY: original = state.committed_state.get(attribute.key, _NO_HISTORY) if original is _NO_HISTORY: if current is NO_VALUE: return cls((), (), ()) else: return cls((), [current], ()) elif current is original and current is not NO_VALUE: return cls((), [current], ()) else: # current convention on related objects is to not # include information # about missing previous value in "deleted", and # to also not include None - the dependency.py rules # ignore the None in any case. if id(original) in _NO_STATE_SYMBOLS or original is None: deleted = () # indicate a "del" operation occurred when we don't have # the previous value as: ([None], (), ()) if id(current) in _NO_STATE_SYMBOLS: current = None else: deleted = [original] if current is NO_VALUE: return cls((), (), deleted) else: return cls([current], (), deleted) @classmethod def from_collection(cls, attribute, state, current): original = state.committed_state.get(attribute.key, _NO_HISTORY) if current is NO_VALUE: return cls((), (), ()) current = getattr(current, "_sa_adapter") if original is NO_VALUE: return cls(list(current), (), ()) elif original is _NO_HISTORY: return cls((), list(current), ()) else: current_states = [ ((c is not None) and instance_state(c) or None, c) for c in current ] original_states = [ ((c is not None) and instance_state(c) or None, c) for c in original ] current_set = dict(current_states) original_set = dict(original_states) return cls( [o for s, o in current_states if s not in original_set], [o for s, o in current_states if s in original_set], [o for s, o in original_states if s not in current_set], ) HISTORY_BLANK = History(None, None, None) def get_history(obj, key, passive=PASSIVE_OFF): """Return a :class:`.History` record for the given object and attribute key. This is the **pre-flush** history for a given attribute, which is reset each time the :class:`.Session` flushes changes to the current database transaction. .. note:: Prefer to use the :attr:`.AttributeState.history` and :meth:`.AttributeState.load_history` accessors to retrieve the :class:`.History` for instance attributes. :param obj: an object whose class is instrumented by the attributes package. :param key: string attribute name. :param passive: indicates loading behavior for the attribute if the value is not already present. This is a bitflag attribute, which defaults to the symbol :attr:`.PASSIVE_OFF` indicating all necessary SQL should be emitted. .. seealso:: :attr:`.AttributeState.history` :meth:`.AttributeState.load_history` - retrieve history using loader callables if the value is not locally present. """ return get_state_history(instance_state(obj), key, passive) def get_state_history(state, key, passive=PASSIVE_OFF): return state.get_history(key, passive) def has_parent(cls, obj, key, optimistic=False): """TODO""" manager = manager_of_class(cls) state = instance_state(obj) return manager.has_parent(state, key, optimistic) def register_attribute(class_, key, **kw): comparator = kw.pop("comparator", None) parententity = kw.pop("parententity", None) doc = kw.pop("doc", None) desc = register_descriptor(class_, key, comparator, parententity, doc=doc) register_attribute_impl(class_, key, **kw) return desc def register_attribute_impl( class_, key, uselist=False, callable_=None, useobject=False, impl_class=None, backref=None, **kw ): manager = manager_of_class(class_) if uselist: factory = kw.pop("typecallable", None) typecallable = manager.instrument_collection_class( key, factory or list ) else: typecallable = kw.pop("typecallable", None) dispatch = manager[key].dispatch if impl_class: impl = impl_class(class_, key, typecallable, dispatch, **kw) elif uselist: impl = CollectionAttributeImpl( class_, key, callable_, dispatch, typecallable=typecallable, **kw ) elif useobject: impl = ScalarObjectAttributeImpl( class_, key, callable_, dispatch, **kw ) else: impl = ScalarAttributeImpl(class_, key, callable_, dispatch, **kw) manager[key].impl = impl if backref: backref_listeners(manager[key], backref, uselist) manager.post_configure_attribute(key) return manager[key] def register_descriptor( class_, key, comparator=None, parententity=None, doc=None ): manager = manager_of_class(class_) descriptor = InstrumentedAttribute( class_, key, comparator=comparator, parententity=parententity ) descriptor.__doc__ = doc manager.instrument_attribute(key, descriptor) return descriptor def unregister_attribute(class_, key): manager_of_class(class_).uninstrument_attribute(key) def init_collection(obj, key): """Initialize a collection attribute and return the collection adapter. This function is used to provide direct access to collection internals for a previously unloaded attribute. e.g.:: collection_adapter = init_collection(someobject, 'elements') for elem in values: collection_adapter.append_without_event(elem) For an easier way to do the above, see :func:`~sqlalchemy.orm.attributes.set_committed_value`. :param obj: a mapped object :param key: string attribute name where the collection is located. """ state = instance_state(obj) dict_ = state.dict return init_state_collection(state, dict_, key) def init_state_collection(state, dict_, key): """Initialize a collection attribute and return the collection adapter. Discards any existing collection which may be there. """ attr = state.manager[key].impl old = dict_.pop(key, None) # discard old collection if old is not None: old_collection = old._sa_adapter attr._dispose_previous_collection(state, old, old_collection, False) user_data = attr._default_value(state, dict_) adapter = attr.get_collection(state, dict_, user_data) adapter._reset_empty() return adapter def set_committed_value(instance, key, value): """Set the value of an attribute with no history events. Cancels any previous history present. The value should be a scalar value for scalar-holding attributes, or an iterable for any collection-holding attribute. This is the same underlying method used when a lazy loader fires off and loads additional data from the database. In particular, this method can be used by application code which has loaded additional attributes or collections through separate queries, which can then be attached to an instance as though it were part of its original loaded state. """ state, dict_ = instance_state(instance), instance_dict(instance) state.manager[key].impl.set_committed_value(state, dict_, value) def set_attribute(instance, key, value, initiator=None): """Set the value of an attribute, firing history events. This function may be used regardless of instrumentation applied directly to the class, i.e. no descriptors are required. Custom attribute management schemes will need to make usage of this method to establish attribute state as understood by SQLAlchemy. :param instance: the object that will be modified :param key: string name of the attribute :param value: value to assign :param initiator: an instance of :class:`.Event` that would have been propagated from a previous event listener. This argument is used when the :func:`.set_attribute` function is being used within an existing event listening function where an :class:`.Event` object is being supplied; the object may be used to track the origin of the chain of events. .. versionadded:: 1.2.3 """ state, dict_ = instance_state(instance), instance_dict(instance) state.manager[key].impl.set(state, dict_, value, initiator) def get_attribute(instance, key): """Get the value of an attribute, firing any callables required. This function may be used regardless of instrumentation applied directly to the class, i.e. no descriptors are required. Custom attribute management schemes will need to make usage of this method to make usage of attribute state as understood by SQLAlchemy. """ state, dict_ = instance_state(instance), instance_dict(instance) return state.manager[key].impl.get(state, dict_) def del_attribute(instance, key): """Delete the value of an attribute, firing history events. This function may be used regardless of instrumentation applied directly to the class, i.e. no descriptors are required. Custom attribute management schemes will need to make usage of this method to establish attribute state as understood by SQLAlchemy. """ state, dict_ = instance_state(instance), instance_dict(instance) state.manager[key].impl.delete(state, dict_) def flag_modified(instance, key): """Mark an attribute on an instance as 'modified'. This sets the 'modified' flag on the instance and establishes an unconditional change event for the given attribute. The attribute must have a value present, else an :class:`.InvalidRequestError` is raised. To mark an object "dirty" without referring to any specific attribute so that it is considered within a flush, use the :func:`.attributes.flag_dirty` call. .. seealso:: :func:`.attributes.flag_dirty` """ state, dict_ = instance_state(instance), instance_dict(instance) impl = state.manager[key].impl impl.dispatch.modified(state, impl._modified_token) state._modified_event(dict_, impl, NO_VALUE, is_userland=True) def flag_dirty(instance): """Mark an instance as 'dirty' without any specific attribute mentioned. This is a special operation that will allow the object to travel through the flush process for interception by events such as :meth:`.SessionEvents.before_flush`. Note that no SQL will be emitted in the flush process for an object that has no changes, even if marked dirty via this method. However, a :meth:`.SessionEvents.before_flush` handler will be able to see the object in the :attr:`.Session.dirty` collection and may establish changes on it, which will then be included in the SQL emitted. .. versionadded:: 1.2 .. seealso:: :func:`.attributes.flag_modified` """ state, dict_ = instance_state(instance), instance_dict(instance) state._modified_event(dict_, None, NO_VALUE, is_userland=True)