Improve "get_collection_count" calls

Reduce the object retrieval to one single field to improve the
collection count.

Bumped neutron-lib to 2.16.0. This version contains [1], needed for
this patch.

[1]https://review.opendev.org/c/openstack/neutron-lib/+/807686

Related-Bug: #1942863

Change-Id: I160e8084e97b23a2bacb49ceb40efbac2d0715be

lower-constraints.txt

@@ -50,7 +50,7 @@ msgpack-python==0.4.0
 munch==2.1.0
 netaddr==0.7.18
 netifaces==0.10.4
-neutron-lib==2.15.0
+neutron-lib==2.16.0
 openstacksdk==0.31.2
 os-client-config==1.28.0
 os-ken==2.2.0

neutron/db/db_base_plugin_v2.py

@@ -563,8 +563,9 @@ class NeutronDbPluginV2(db_base_plugin_common.DbBasePluginCommon,
 
     @db_api.retry_if_session_inactive()
     def get_networks_count(self, context, filters=None):
-        return model_query.get_collection_count(context, models_v2.Network,
-                                                filters=filters)
+        return model_query.get_collection_count(
+            context, models_v2.Network, filters=filters,
+            query_field=models_v2.Network.id.key)
 
     @db_api.retry_if_session_inactive()
     def create_subnet_bulk(self, context, subnets):

neutron/db/l3_db.py

@@ -615,8 +615,9 @@ class L3_NAT_dbonly_mixin(l3.RouterPluginBase,
 
     @db_api.retry_if_session_inactive()
     def get_routers_count(self, context, filters=None):
-        return model_query.get_collection_count(context, l3_models.Router,
-                                                filters=filters)
+        return model_query.get_collection_count(
+            context, l3_models.Router, filters=filters,
+            query_field=l3_models.Router.id.key)
 
     def _check_for_dup_router_subnets(self, context, router,
                                       network_id, new_subnets):

requirements.txt

@@ -16,7 +16,7 @@ Jinja2>=2.10 # BSD License (3 clause)
 keystonemiddleware>=5.1.0 # Apache-2.0
 netaddr>=0.7.18 # BSD
 netifaces>=0.10.4 # MIT
-neutron-lib>=2.15.0 # Apache-2.0
+neutron-lib>=2.16.0 # Apache-2.0
 python-neutronclient>=6.7.0 # Apache-2.0
 tenacity>=6.0.0 # Apache-2.0
 SQLAlchemy>=1.4.23 # MIT