DB: sorting on elements which are AssociationProxy fails

[Daniel Alvarez]

If I do a DB query trying to sort by a column which is an AssociationProxy I get the following exception:

Nov 20 14:41:20 centos.rdocloud neutron-server[11934]: ERROR neutron.plugins.ml2.managers File "/opt/stack/neutron/neutron/db/db_base_plugin_v2.py", line 1438, in get_ports
Nov 20 14:41:20 centos.rdocloud neutron-server[11934]: ERROR neutron.plugins.ml2.managers page_reverse=page_reverse)
Nov 20 14:41:20 centos.rdocloud neutron-server[11934]: ERROR neutron.plugins.ml2.managers File "/opt/stack/neutron/neutron/plugins/ml2/plugin.py", line 1935, in _get_ports_qu
Nov 20 14:41:20 centos.rdocloud neutron-server[11934]: ERROR neutron.plugins.ml2.managers *args, **kwargs)
Nov 20 14:41:20 centos.rdocloud neutron-server[11934]: ERROR neutron.plugins.ml2.managers File "/opt/stack/neutron/neutron/db/db_base_plugin_v2.py", line 1418, in _get_ports_
Nov 20 14:41:20 centos.rdocloud neutron-server[11934]: ERROR neutron.plugins.ml2.managers *args, **kwargs)
Nov 20 14:41:20 centos.rdocloud neutron-server[11934]: ERROR neutron.plugins.ml2.managers File "/opt/stack/neutron/neutron/db/_model_query.py", line 159, in get_collection_qu
Nov 20 14:41:20 centos.rdocloud neutron-server[11934]: ERROR neutron.plugins.ml2.managers sort_keys = db_utils.get_and_validate_sort_keys(sorts, model)
Nov 20 14:41:20 centos.rdocloud neutron-server[11934]: ERROR neutron.plugins.ml2.managers File "/usr/lib/python2.7/site-packages/neutron_lib/db/utils.py", line 45, in get_and
Nov 20 14:41:20 centos.rdocloud neutron-server[11934]: ERROR neutron.plugins.ml2.managers if isinstance(sort_key_attr.property,
Nov 20 14:41:20 centos.rdocloud neutron-server[11934]: ERROR neutron.plugins.ml2.managers AttributeError: 'AssociationProxy' object has no attribute 'property'
Nov 20 14:41:20 centos.rdocloud neutron-server[11934]: ERROR neutron.plugins.ml2.managers

This is reproducible for example by querying ports sorted by 'created_at' attribute:

ports = self._plugin.get_ports(context, sorts=[('created_at', True)])

Looks like we may need to special case the AssociationProxy columns such as we already do in the filtering code at:

https://github.com/openstack/neutron/blob/0bb6136919a31751242d2efbefedbd8922b6bd0a/neutron/db/_model_query.py#L88

[Mike Bayer (zzzeek)]

association proxies represent a link to another table so a simple "order_by()" is not so simple, and is not supported by SQLAlchemy. if we did make it supported, it would involve ordering by a correlated subquery which would be very inefficient in any case.

So I think the check at http://git.openstack.org/cgit/openstack/neutron-lib/tree/neutron_lib/db/utils.py#n45 should be fixed to also reject assocaition proxies, and if you need to ORDER BY the attribute that a proxy refers towards, you should be creating the JOIN that you need and ORDER BY the actual column attribute.

[pandatt (pandatt)]

Seems to duplicated with issue: https://bugs.launchpad.net/neutron/+bug/1659175

[pandatt (pandatt)]

See the patch: https://review.opendev.org/#/c/653903/