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dynamic.py
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# orm/dynamic.py # Copyright (C) 2005-2021 the SQLAlchemy authors and contributors # <see AUTHORS file> # # This module is part of SQLAlchemy and is released under # the MIT License: http://www.opensource.org/licenses/mit-license.php """Dynamic collection API. Dynamic collections act like Query() objects for read operations and support basic add/delete mutation. """ from . import attributes from . import exc as orm_exc from . import interfaces from . import object_mapper from . import object_session from . import properties from . import strategies from . import util as orm_util from .query import Query from .. import exc from .. import log from .. import util @log.class_logger @properties.RelationshipProperty.strategy_for(lazy="dynamic") class DynaLoader(strategies.AbstractRelationshipLoader): def init_class_attribute(self, mapper): self.is_class_level = True if not self.uselist: raise exc.InvalidRequestError( "On relationship %s, 'dynamic' loaders cannot be used with " "many-to-one/one-to-one relationships and/or " "uselist=False." % self.parent_property ) elif self.parent_property.direction not in ( interfaces.ONETOMANY, interfaces.MANYTOMANY, ): util.warn( "On relationship %s, 'dynamic' loaders cannot be used with " "many-to-one/one-to-one relationships and/or " "uselist=False. This warning will be an exception in a " "future release." % self.parent_property ) strategies._register_attribute( self.parent_property, mapper, useobject=True, impl_class=DynamicAttributeImpl, target_mapper=self.parent_property.mapper, order_by=self.parent_property.order_by, query_class=self.parent_property.query_class, ) class DynamicAttributeImpl(attributes.AttributeImpl): uses_objects = True default_accepts_scalar_loader = False supports_population = False collection = False dynamic = True def __init__( self, class_, key, typecallable, dispatch, target_mapper, order_by, query_class=None, **kw ): super(DynamicAttributeImpl, self).__init__( class_, key, typecallable, dispatch, **kw ) self.target_mapper = target_mapper self.order_by = order_by if not query_class: self.query_class = AppenderQuery elif AppenderMixin in query_class.mro(): self.query_class = query_class else: self.query_class = mixin_user_query(query_class) def get(self, state, dict_, passive=attributes.PASSIVE_OFF): if not passive & attributes.SQL_OK: return self._get_collection_history( state, attributes.PASSIVE_NO_INITIALIZE ).added_items else: return self.query_class(self, state) def get_collection( self, state, dict_, user_data=None, passive=attributes.PASSIVE_NO_INITIALIZE, ): if not passive & attributes.SQL_OK: return self._get_collection_history(state, passive).added_items else: history = self._get_collection_history(state, passive) return history.added_plus_unchanged @util.memoized_property def _append_token(self): return attributes.Event(self, attributes.OP_APPEND) @util.memoized_property def _remove_token(self): return attributes.Event(self, attributes.OP_REMOVE) def fire_append_event( self, state, dict_, value, initiator, collection_history=None ): if collection_history is None: collection_history = self._modified_event(state, dict_) collection_history.add_added(value) for fn in self.dispatch.append: value = fn(state, value, initiator or self._append_token) if self.trackparent and value is not None: self.sethasparent(attributes.instance_state(value), state, True) def fire_remove_event( self, state, dict_, value, initiator, collection_history=None ): if collection_history is None: collection_history = self._modified_event(state, dict_) collection_history.add_removed(value) if self.trackparent and value is not None: self.sethasparent(attributes.instance_state(value), state, False) for fn in self.dispatch.remove: fn(state, value, initiator or self._remove_token) def _modified_event(self, state, dict_): if self.key not in state.committed_state: state.committed_state[self.key] = CollectionHistory(self, state) state._modified_event(dict_, self, attributes.NEVER_SET) # this is a hack to allow the fixtures.ComparableEntity fixture # to work dict_[self.key] = True return state.committed_state[self.key] def set( self, state, dict_, value, initiator=None, passive=attributes.PASSIVE_OFF, check_old=None, pop=False, _adapt=True, ): if initiator and initiator.parent_token is self.parent_token: return if pop and value is None: return iterable = value new_values = list(iterable) if state.has_identity: old_collection = util.IdentitySet(self.get(state, dict_)) collection_history = self._modified_event(state, dict_) if not state.has_identity: old_collection = collection_history.added_items else: old_collection = old_collection.union( collection_history.added_items ) idset = util.IdentitySet constants = old_collection.intersection(new_values) additions = idset(new_values).difference(constants) removals = old_collection.difference(constants) for member in new_values: if member in additions: self.fire_append_event( state, dict_, member, None, collection_history=collection_history, ) for member in removals: self.fire_remove_event( state, dict_, member, None, collection_history=collection_history, ) def delete(self, *args, **kwargs): raise NotImplementedError() def set_committed_value(self, state, dict_, value): raise NotImplementedError( "Dynamic attributes don't support " "collection population." ) def get_history(self, state, dict_, passive=attributes.PASSIVE_OFF): c = self._get_collection_history(state, passive) return c.as_history() def get_all_pending( self, state, dict_, passive=attributes.PASSIVE_NO_INITIALIZE ): c = self._get_collection_history(state, passive) return [(attributes.instance_state(x), x) for x in c.all_items] def _get_collection_history(self, state, passive=attributes.PASSIVE_OFF): if self.key in state.committed_state: c = state.committed_state[self.key] else: c = CollectionHistory(self, state) if state.has_identity and (passive & attributes.INIT_OK): return CollectionHistory(self, state, apply_to=c) else: return c def append( self, state, dict_, value, initiator, passive=attributes.PASSIVE_OFF ): if initiator is not self: self.fire_append_event(state, dict_, value, initiator) def remove( self, state, dict_, value, initiator, passive=attributes.PASSIVE_OFF ): if initiator is not self: self.fire_remove_event(state, dict_, value, initiator) def pop( self, state, dict_, value, initiator, passive=attributes.PASSIVE_OFF ): self.remove(state, dict_, value, initiator, passive=passive) class AppenderMixin(object): query_class = None def __init__(self, attr, state): super(AppenderMixin, self).__init__(attr.target_mapper, None) self.instance = instance = state.obj() self.attr = attr mapper = object_mapper(instance) prop = mapper._props[self.attr.key] if prop.secondary is not None: # this is a hack right now. The Query only knows how to # make subsequent joins() without a given left-hand side # from self._from_obj[0]. We need to ensure prop.secondary # is in the FROM. So we purposely put the mapper selectable # in _from_obj[0] to ensure a user-defined join() later on # doesn't fail, and secondary is then in _from_obj[1]. self._from_obj = (prop.mapper.selectable, prop.secondary) self._criterion = prop._with_parent(instance, alias_secondary=False) if self.attr.order_by: self._order_by = self.attr.order_by def session(self): sess = object_session(self.instance) if ( sess is not None and self.autoflush and sess.autoflush and self.instance in sess ): sess.flush() if not orm_util.has_identity(self.instance): return None else: return sess session = property(session, lambda s, x: None) def __iter__(self): sess = self.session if sess is None: return iter( self.attr._get_collection_history( attributes.instance_state(self.instance), attributes.PASSIVE_NO_INITIALIZE, ).added_items ) else: return iter(self._clone(sess)) def __getitem__(self, index): sess = self.session if sess is None: return self.attr._get_collection_history( attributes.instance_state(self.instance), attributes.PASSIVE_NO_INITIALIZE, ).indexed(index) else: return self._clone(sess).__getitem__(index) def count(self): sess = self.session if sess is None: return len( self.attr._get_collection_history( attributes.instance_state(self.instance), attributes.PASSIVE_NO_INITIALIZE, ).added_items ) else: return self._clone(sess).count() def _clone(self, sess=None): # note we're returning an entirely new Query class instance # here without any assignment capabilities; the class of this # query is determined by the session. instance = self.instance if sess is None: sess = object_session(instance) if sess is None: raise orm_exc.DetachedInstanceError( "Parent instance %s is not bound to a Session, and no " "contextual session is established; lazy load operation " "of attribute '%s' cannot proceed" % (orm_util.instance_str(instance), self.attr.key) ) if self.query_class: query = self.query_class(self.attr.target_mapper, session=sess) else: query = sess.query(self.attr.target_mapper) query._criterion = self._criterion query._from_obj = self._from_obj query._order_by = self._order_by return query def extend(self, iterator): for item in iterator: self.attr.append( attributes.instance_state(self.instance), attributes.instance_dict(self.instance), item, None, ) def append(self, item): self.attr.append( attributes.instance_state(self.instance), attributes.instance_dict(self.instance), item, None, ) def remove(self, item): self.attr.remove( attributes.instance_state(self.instance), attributes.instance_dict(self.instance), item, None, ) class AppenderQuery(AppenderMixin, Query): """A dynamic query that supports basic collection storage operations.""" def mixin_user_query(cls): """Return a new class with AppenderQuery functionality layered over.""" name = "Appender" + cls.__name__ return type(name, (AppenderMixin, cls), {"query_class": cls}) class CollectionHistory(object): """Overrides AttributeHistory to receive append/remove events directly.""" def __init__(self, attr, state, apply_to=None): if apply_to: coll = AppenderQuery(attr, state).autoflush(False) self.unchanged_items = util.OrderedIdentitySet(coll) self.added_items = apply_to.added_items self.deleted_items = apply_to.deleted_items self._reconcile_collection = True else: self.deleted_items = util.OrderedIdentitySet() self.added_items = util.OrderedIdentitySet() self.unchanged_items = util.OrderedIdentitySet() self._reconcile_collection = False @property def added_plus_unchanged(self): return list(self.added_items.union(self.unchanged_items)) @property def all_items(self): return list( self.added_items.union(self.unchanged_items).union( self.deleted_items ) ) def as_history(self): if self._reconcile_collection: added = self.added_items.difference(self.unchanged_items) deleted = self.deleted_items.intersection(self.unchanged_items) unchanged = self.unchanged_items.difference(deleted) else: added, unchanged, deleted = ( self.added_items, self.unchanged_items, self.deleted_items, ) return attributes.History(list(added), list(unchanged), list(deleted)) def indexed(self, index): return list(self.added_items)[index] def add_added(self, value): self.added_items.add(value) def add_removed(self, value): if value in self.added_items: self.added_items.remove(value) else: self.deleted_items.add(value)