def load_one_to_manys(session): # TODO(kevinbenton): we should be able to remove this after we # have eliminated all places where related objects are constructed # using a key rather than a relationship. for new_object in session.new: state = sqlalchemy.inspect(new_object) # set up relationship loading so that we can call lazy # loaders on the object even though the ".key" is not set up yet # (normally happens by in after_flush_postexec, but we're trying # to do this more succinctly). in this context this is only # setting a simple flag on the object's state. session.enable_relationship_loading(new_object) # look for eager relationships and do normal load. # For relationships where the related object is also # in the session these lazy loads will pull from the # identity map and not emit SELECT. Otherwise, we are still # local in the transaction so a normal SELECT load will work fine. for relationship_attr in state.mapper.relationships: if relationship_attr.lazy not in ('joined', 'subquery'): # we only want to automatically load relationships that would # automatically load during a lookup operation continue if relationship_attr.key not in state.dict: getattr(new_object, relationship_attr.key) assert relationship_attr.key in state.dict
def _persistent_to_deleted(session, obj): """Expire relationships when an object w/ a foreign key becomes deleted""" mapper = sqlalchemy.inspect(obj).mapper for prop in mapper.relationships: if prop.direction is orm.interfaces.MANYTOONE: for col in prop.local_columns: colkey = mapper.get_property_by_column(col).key expire_for_fk_change(obj, None, prop, colkey)
def _persistent_to_deleted(session, obj): """Expire relationships when an object w/ a foreign key becomes deleted""" mapper = sqlalchemy.inspect(obj).mapper for prop in mapper.relationships: if prop.direction is orm.interfaces.MANYTOONE: for col in prop.local_columns: colkey = mapper.get_property_by_column(col).key _expire_for_fk_change(obj, None, prop, colkey)
def expire_for_fk_change(target, fk_value, relationship_prop, column_attr): """Expire relationship attributes when a many-to-one column changes.""" sess = orm.object_session(target) # subnets and network's many-to-one relationship is used as example in the # comments in this function if sess is not None: # optional behavior #1 - expire the "Network.subnets" # collection on the existing "network" object if relationship_prop.back_populates and \ relationship_prop.key in target.__dict__: obj = getattr(target, relationship_prop.key) if obj is not None and sqlalchemy.inspect(obj).persistent: sess.expire(obj, [relationship_prop.back_populates]) # optional behavior #2 - expire the "Subnet.network" if sqlalchemy.inspect(target).persistent: sess.expire(target, [relationship_prop.key]) # optional behavior #3 - "trick" the ORM by actually # setting the value ahead of time, then emitting a load # for the attribute so that the *new* Subnet.network # is loaded. Then, expire Network.subnets on *that*. # Other techniques here including looking in the identity # map for "value", if this is a simple many-to-one get. if relationship_prop.back_populates: target.__dict__[column_attr] = fk_value new = getattr(target, relationship_prop.key) if new is not None: if sqlalchemy.inspect(new).persistent: sess.expire(new, [relationship_prop.back_populates]) else: # no Session yet, do it later. This path is reached from the 'expire' # listener setup by '_expire_prop_on_col' below, when a foreign key # is directly assigned to in the many to one side of a relationship. # i.e. assigning directly to Subnet.network_id before Subnet is added # to the session if target not in _emit_on_pending: _emit_on_pending[target] = [] _emit_on_pending[target].append( (fk_value, relationship_prop, column_attr))
def _expire_for_fk_change(target, fk_value, relationship_prop, column_attr): """Expire relationship attributes when a many-to-one column changes.""" sess = orm.object_session(target) # subnets and network's many-to-one relationship is used as example in the # comments in this function if sess is not None: # optional behavior #1 - expire the "Network.subnets" # collection on the existing "network" object if relationship_prop.back_populates and \ relationship_prop.key in target.__dict__: obj = getattr(target, relationship_prop.key) if obj is not None and sqlalchemy.inspect(obj).persistent: sess.expire(obj, [relationship_prop.back_populates]) # optional behavior #2 - expire the "Subnet.network" if sqlalchemy.inspect(target).persistent: sess.expire(target, [relationship_prop.key]) # optional behavior #3 - "trick" the ORM by actually # setting the value ahead of time, then emitting a load # for the attribute so that the *new* Subnet.network # is loaded. Then, expire Network.subnets on *that*. # Other techniques here including looking in the identity # map for "value", if this is a simple many-to-one get. if relationship_prop.back_populates: target.__dict__[column_attr] = fk_value new = getattr(target, relationship_prop.key) if new is not None: if sqlalchemy.inspect(new).persistent: sess.expire(new, [relationship_prop.back_populates]) else: # no Session yet, do it later. This path is reached from the 'expire' # listener setup by '_expire_prop_on_col' below, when a foreign key # is directly assigned to in the many to one side of a relationship. # i.e. assigning directly to Subnet.network_id before Subnet is added # to the session if target not in _emit_on_pending: _emit_on_pending[target] = [] _emit_on_pending[target].append( (fk_value, relationship_prop, column_attr))
def load_one_to_manys(session): # TODO(kevinbenton): we should be able to remove this after we # have eliminated all places where related objects are constructed # using a key rather than a relationship. # capture any new objects if session.new: session.flush() if session.transaction.nested: # wait until final commit return for new_object in session.info.pop('_load_rels', []): if new_object not in session: # don't load detached objects because that brings them back into # session continue state = sqlalchemy.inspect(new_object) # set up relationship loading so that we can call lazy # loaders on the object even though the ".key" is not set up yet # (normally happens by in after_flush_postexec, but we're trying # to do this more succinctly). in this context this is only # setting a simple flag on the object's state. session.enable_relationship_loading(new_object) # look for eager relationships and do normal load. # For relationships where the related object is also # in the session these lazy loads will pull from the # identity map and not emit SELECT. Otherwise, we are still # local in the transaction so a normal SELECT load will work fine. for relationship_attr in state.mapper.relationships: if relationship_attr.lazy not in ('joined', 'subquery'): # we only want to automatically load relationships that would # automatically load during a lookup operation continue if relationship_attr.key not in state.dict: getattr(new_object, relationship_attr.key) if relationship_attr.key not in state.dict: msg = ("Relationship %s attributes must be loaded in db" " object %s" % (relationship_attr.key, state.dict)) raise AssertionError(msg)
def load_one_to_manys(session): # TODO(kevinbenton): we should be able to remove this after we # have eliminated all places where related objects are constructed # using a key rather than a relationship. # capture any new objects if session.new: session.flush() if session.transaction.nested: # wait until final commit return for new_object in session.info.pop('_load_rels', []): if new_object not in session: # don't load detached objects because that brings them back into # session continue state = sqlalchemy.inspect(new_object) # set up relationship loading so that we can call lazy # loaders on the object even though the ".key" is not set up yet # (normally happens by in after_flush_postexec, but we're trying # to do this more succinctly). in this context this is only # setting a simple flag on the object's state. session.enable_relationship_loading(new_object) # look for eager relationships and do normal load. # For relationships where the related object is also # in the session these lazy loads will pull from the # identity map and not emit SELECT. Otherwise, we are still # local in the transaction so a normal SELECT load will work fine. for relationship_attr in state.mapper.relationships: if relationship_attr.lazy not in ('joined', 'subquery'): # we only want to automatically load relationships that would # automatically load during a lookup operation continue if relationship_attr.key not in state.dict: getattr(new_object, relationship_attr.key) if relationship_attr.key not in state.dict: msg = ("Relationship %s attributes must be loaded in db" " object %s" % (relationship_attr.key, state.dict)) raise AssertionError(msg)
def _listen_for_changes(cls, key, inst): mapper = sqlalchemy.inspect(cls) if key not in mapper.relationships: return prop = inst.property if prop.direction is orm.interfaces.MANYTOONE: for col in prop.local_columns: colkey = mapper.get_property_by_column(col).key _expire_prop_on_col(cls, prop, colkey) elif prop.direction is orm.interfaces.ONETOMANY: remote_mapper = prop.mapper # the collection *has* to have a MANYTOONE backref so we # can look up the parent. so here we make one if it doesn't # have it already, as is the case in this example if not prop.back_populates: name = "_%s_backref" % prop.key backref_prop = orm.relationship( prop.parent, back_populates=prop.key) remote_mapper.add_property(name, backref_prop) prop.back_populates = name
def _listen_for_changes(cls, key, inst): mapper = sqlalchemy.inspect(cls) if key not in mapper.relationships: return prop = inst.property if prop.direction is orm.interfaces.MANYTOONE: for col in prop.local_columns: colkey = mapper.get_property_by_column(col).key _expire_prop_on_col(cls, prop, colkey) elif prop.direction is orm.interfaces.ONETOMANY: remote_mapper = prop.mapper # the collection *has* to have a MANYTOONE backref so we # can look up the parent. so here we make one if it doesn't # have it already, as is the case in this example if not prop.back_populates: name = "_%s_backref" % prop.key backref_prop = orm.relationship(prop.parent, back_populates=prop.key) remote_mapper.add_property(name, backref_prop) prop.back_populates = name