146 lines
6.0 KiB
Python
146 lines
6.0 KiB
Python
# Copyright 2011 VMware, Inc.
|
|
# All Rights Reserved.
|
|
#
|
|
# Licensed under the Apache License, Version 2.0 (the "License"); you may
|
|
# not use this file except in compliance with the License. You may obtain
|
|
# a copy of the License at
|
|
#
|
|
# http://www.apache.org/licenses/LICENSE-2.0
|
|
#
|
|
# Unless required by applicable law or agreed to in writing, software
|
|
# distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
|
|
# WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
|
|
# License for the specific language governing permissions and limitations
|
|
# under the License.
|
|
|
|
import weakref
|
|
|
|
from neutron_lib.db import model_base
|
|
import sqlalchemy
|
|
from sqlalchemy import event # noqa
|
|
from sqlalchemy import orm
|
|
|
|
|
|
# Expire relationships when foreign key changes.
|
|
#
|
|
# NOTE(ihrachys) Arguably, it's a sqlalchemy anti-pattern to access child
|
|
# models directly and through parent relationships in the same session. But
|
|
# since OVO mechanism is built around synthetic fields that assume this mixed
|
|
# access is possible, we keep it here until we find a way to migrate OVO
|
|
# synthetic fields to better mechanism that would update child models via
|
|
# parents. Even with that, there are multiple places in plugin code where we
|
|
# mix access when using models directly; those occurrences would need to be
|
|
# fixed too to be able to remove this hook and explicit expire() calls.
|
|
#
|
|
# Adopted from the following recipe:
|
|
# https://bitbucket.org/zzzeek/sqlalchemy/wiki/UsageRecipes
|
|
# /ExpireRelationshipOnFKChange
|
|
#
|
|
# ...then massively changed to actually work for all neutron backref cases.
|
|
#
|
|
# TODO(ihrachys) at some point these event handlers should be extended to also
|
|
# automatically refresh values for expired attributes
|
|
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))
|
|
|
|
|
|
_emit_on_pending = weakref.WeakKeyDictionary()
|
|
|
|
|
|
@event.listens_for(orm.session.Session, "pending_to_persistent")
|
|
def _pending_callables(session, obj):
|
|
"""Expire relationships when a new object w/ a foreign key becomes
|
|
persistent
|
|
"""
|
|
if obj is None:
|
|
return
|
|
args = _emit_on_pending.pop(obj, [])
|
|
for a in args:
|
|
if a is not None:
|
|
_expire_for_fk_change(obj, *a)
|
|
|
|
|
|
@event.listens_for(orm.session.Session, "persistent_to_deleted")
|
|
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)
|
|
|
|
|
|
@event.listens_for(model_base.BASEV2, "attribute_instrument", propagate=True)
|
|
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 _expire_prop_on_col(cls, prop, colkey):
|
|
@event.listens_for(getattr(cls, colkey), "set")
|
|
def expire(target, value, oldvalue, initiator):
|
|
"""Expire relationships when the foreign key attribute on
|
|
an object changes
|
|
"""
|
|
_expire_for_fk_change(target, value, prop, colkey)
|