Database deletions should use delete orphan

[Gary Kotton]

Following a review on cascade='delete', the following was suggested:

"Typically, cascade is usually left at its default, or configured as all, delete-orphan, indicating the child objects should be treated as “owned” by the parent."

[Senhua Huang (senhuang)]

Hi Gary,

Do you mean we should add "delete-orphan" to cascade in the following lines (141-146) of codes in quantum/db/models_v2.py:
dns_nameservers = orm.relationship(DNSNameServer, backref='subnet', cascade='delete')
routes = orm.relationship(Route, backref='subnet', cascade='delete')

and the following lines (68-75) in quantum/db/security_groups_db.py:
security_group = orm.relationship(securityGroup, backref=orm.backref('rules', cascade='all, delete'), primaryjoin="SecurityGroup.id==SecurityGroupRule.security_group_id")
source_group = orm.relationship(SecurityGroup, backref=orm.backref('source_rules, cascade='all,delete'), primaryjoin="SecurityGroup.id==SecurityGroupRule.source_group_id")?

According to the online document of SqlAlchemy, "delete-orphan cascade implies that each child object can only have one parent at a time, so is configured in the vast majority of cases on a one-to-many relationship." Is this the case here for the relationship defined by dns_nameservers, routes, security_group, and source_group? Thanks!

[yong sheng gong (gongysh)]

Hi,
When it means owned by parent, all, delete-orphan should be used.
dns_nameservers, routers should be owned by one parent. but source_groups should be not this case(IMHO). securitygrouprules should be owned by only security group.

[dan wendlandt (danwent)]

note: this change should not be merged into grizzly, but you are free to work on it for later submission to havana.

[Senhua Huang (senhuang)]

okay. thanks!

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/24501

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/24501
Committed: http://github.com/openstack/quantum/commit/377f78fa55988a92674bd940130ff8d15f3ec521
Submitter: Jenkins
Branch: master

commit 377f78fa55988a92674bd940130ff8d15f3ec521
Author: Senhua Huang <email address hidden>
Date: Thu Mar 14 19:05:38 2013 -0700

    Adds delete-orphan to database deletion.

    Change-Id: I3570c812c042365e68eef3b5463899afa85eb9fd
    Fixes: bug #1096549