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