Tune up db.instance_get_all_uuids_by_hosts

When instance_get_all_uuids_by_hosts was added [1] some follow up
cleanups where suggested. This change provides them:

* removal of redundance in docstring
* moving docstring to the public method, rather than the private
  implementation
* more clarity on the type of the default (defaultdict(list)) and
  the implications thereof
* Using an sa.bindparam in the 'in_' call. This requires that the
  SQLAlchemy requirment be raised to at least 1.2.0 where the feature
  was added. 1.2.19, the latest bugfix release, is chosen.

[1] If92fe8b75d20a738f37e2a74c52c59bfc699a74f

Change-Id: Ib538ab070d73b06ddeb9fea3af149304e40952ec

lower-constraints.txt

@@ -145,7 +145,7 @@ simplejson==3.13.2
 six==1.10.0
 smmap2==2.0.3
 sortedcontainers==2.1.0
-SQLAlchemy==1.0.10
+SQLAlchemy==1.2.19
 sqlalchemy-migrate==0.11.0
 sqlparse==0.2.4
 statsd==3.2.2

nova/db/sqlalchemy/api.py

@@ -2659,28 +2659,28 @@ def instance_get_all_by_host(context, host, columns_to_join=None):
 
 
 def _instance_get_all_uuids_by_hosts(context, hosts):
-    """Return a dict, keyed by hostname, of a list of the instance uuids on the
-    host for each supplied hostname.
-
-    Returns a dict, keyed by hostname, of a list of UUIDs, not Instance model
-    objects.
-    """
     itbl = models.Instance.__table__
     default_deleted_value = itbl.c.deleted.default.arg
     sel = sql.select([itbl.c.host, itbl.c.uuid])
     sel = sel.where(sql.and_(
             itbl.c.deleted == default_deleted_value,
-            itbl.c.host.in_(hosts)))
+            itbl.c.host.in_(sa.bindparam('hosts', expanding=True))))
 
     # group the instance UUIDs by hostname
     res = collections.defaultdict(list)
-    for rec in context.session.execute(sel).fetchall():
+    for rec in context.session.execute(sel, {'hosts': hosts}).fetchall():
         res[rec[0]].append(rec[1])
     return res
 
 
 @pick_context_manager_reader
 def instance_get_all_uuids_by_hosts(context, hosts):
+    """Return a dict, keyed by hostname, of a list of the instance uuids on the
+    host for each supplied hostname, not Instance model objects.
+
+    The dict is a defaultdict of list, thus inspecting the dict for a host not
+    in the dict will return an empty list not a KeyError.
+    """
     return _instance_get_all_uuids_by_hosts(context, hosts)
 
 

nova/objects/instance.py

@@ -1430,8 +1430,7 @@ class InstanceList(base.ObjectListBase, base.NovaObject):
 
     @base.remotable_classmethod
     def get_uuids_by_host(cls, context, host):
-        return db.instance_get_all_uuids_by_hosts(context, [host]).get(
-            host, [])
+        return db.instance_get_all_uuids_by_hosts(context, [host])[host]
 
     @base.remotable_classmethod
     def get_uuids_by_hosts(cls, context, hosts):

nova/tests/unit/db/test_db_api.py

@@ -362,8 +362,8 @@ class UnsupportedDbRegexpTestCase(DbTestCase):
         test2 = self.create_instance_with_args(display_name='test2')
         test3 = self.create_instance_with_args(display_name='test3')
         uuids = [i.uuid for i in (test1, test2, test3)]
-        results = db.instance_get_all_uuids_by_hosts(self.context,
-                                                         [test1.host])
+        results = db.instance_get_all_uuids_by_hosts(
+            self.context, [test1.host])
         self.assertEqual(1, len(results))
         self.assertIn(test1.host, results)
         found_uuids = results[test1.host]

nova/tests/unit/objects/test_instance.py

@@ -12,6 +12,7 @@
 #    License for the specific language governing permissions and limitations
 #    under the License.
 
+import collections
 import datetime
 import six
 
@@ -1915,7 +1916,7 @@ class _TestInstanceListObject(object):
 
     @mock.patch('nova.db.api.instance_get_all_uuids_by_hosts')
     def test_get_uuids_by_host_no_match(self, mock_get_all):
-        mock_get_all.return_value = {}
+        mock_get_all.return_value = collections.defaultdict(list)
         actual_uuids = objects.InstanceList.get_uuids_by_host(
             self.context, 'b')
         self.assertEqual([], actual_uuids)

requirements.txt

@@ -3,7 +3,7 @@
 # process, which may cause wedges in the gate later.
 
 pbr!=2.1.0,>=2.0.0 # Apache-2.0
-SQLAlchemy!=1.1.5,!=1.1.6,!=1.1.7,!=1.1.8,>=1.0.10 # MIT
+SQLAlchemy>=1.2.19 # MIT
 decorator>=3.4.0 # BSD
 eventlet!=0.20.1,>=0.20.0 # MIT
 Jinja2>=2.10 # BSD License (3 clause)