# orm/dynamic.py # Copyright (C) 2005-2013 the SQLAlchemy authors and contributors # # 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 log, util, exc from ..sql import operators from . import ( attributes, object_session, util as orm_util, strategies, object_mapper, exc as orm_exc ) from .query import Query 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) strategies._register_attribute(self, mapper, useobject=True, uselist=True, impl_class=DynamicAttributeImpl, target_mapper=self.parent_property.mapper, order_by=self.parent_property.order_by, query_class=self.parent_property.query_class, backref=self.parent_property.back_populates, ) log.class_logger(DynaLoader) class DynamicAttributeImpl(attributes.AttributeImpl): uses_objects = True accepts_scalar_loader = False supports_population = False collection = False 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 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) 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) 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, passive=attributes.PASSIVE_OFF, check_old=None, pop=False): if initiator and initiator.parent_token is self.parent_token: return if pop and value is None: return self._set_iterable(state, dict_, value) def _set_iterable(self, state, dict_, iterable, adapter=None): 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_): c = self._get_collection_history( state, attributes.PASSIVE_NO_INITIALIZE) 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] self._criterion = prop.compare( operators.eq, instance, value_is_parent=True, 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._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)