diff --git a/neutron/db/_model_query.py b/neutron/db/_model_query.py
new file mode 100644
index 00000000000..be43258c47e
--- /dev/null
+++ b/neutron/db/_model_query.py
@@ -0,0 +1,125 @@
+#    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.
+
+
+"""
+NOTE: This module shall not be used by external projects. It will be moved
+      to neutron-lib in due course, and then it can be used from there.
+"""
+
+from neutron.common import utils
+
+# Classes implementing extensions will register hooks into this dictionary
+# for "augmenting" the "core way" of building a query for retrieving objects
+# from a model class. Hooks are registered by invoking register_hook().
+_model_query_hooks = {
+    # model1 : {
+    #              hook1: {
+    #                         'query': query_hook,
+    #                         'filter': filter_hook,
+    #                         'result_filters': result_filters
+    #              },
+    #              hook2: {
+    #                         'query': query_hook,
+    #                         'filter': filter_hook,
+    #                         'result_filters': result_filters
+    #              },
+    #              ...
+    #          },
+    # model2 : {
+    #              hook1: {
+    #                         'query': query_hook,
+    #                         'filter': filter_hook,
+    #                         'result_filters': result_filters
+    #              },
+    #              hook2: {
+    #                         'query': query_hook,
+    #                         'filter': filter_hook,
+    #                         'result_filters': result_filters
+    #              },
+    #              ...
+    #          },
+    # ...
+}
+
+
+def register_hook(model, name, query_hook, filter_hook,
+                  result_filters=None):
+    """Register a hook to be invoked when a query is executed.
+
+    :param model: The DB Model that the hook applies to.
+    :type model: sqlalchemy orm model
+
+    :param name: A name for the hook.
+    :type name: str
+
+    :param query_hook: The method to be called to augment the query.
+    :type query_hook: callable or None
+
+    :param filter_hook: A method to be called to augment the query filter.
+    :type filter_hook: callable or None
+
+    :param result_filters: A Method to be called to filter the query result.
+    :type result_filters: callable or None
+
+    Adds the hook components to the _model_query_hooks dict. Models are the
+    keys of this dict, whereas the value is another dict mapping hook names
+    to callables performing the hook.
+
+    Each hook has three components:
+        "query", used to build the query expression
+        "filter", used to build the filter expression
+        "result_filters", used for final filtering on the query result
+
+    Query hooks take as input the query being built and return a
+    transformed query expression.
+        def mymodel_query_hook(context, original_model, query):
+            augmented_query = ...
+            return augmented_query
+
+    Filter hooks take as input the filter expression being built and return
+    a transformed filter expression
+        def mymodel_filter_hook(context, original_model, filters):
+            refined_filters = ...
+            return refined_filters
+
+    Result filter hooks take as input the query expression and the filter
+    expression, and return a final transformed query expression.
+        def mymodel_result_filter_hook(query, filters):
+            final_filters = ...
+            return query.filter(final_filters)
+
+    """
+    if callable(query_hook):
+        query_hook = utils.make_weak_ref(query_hook)
+    if callable(filter_hook):
+        filter_hook = utils.make_weak_ref(filter_hook)
+    if callable(result_filters):
+        result_filters = utils.make_weak_ref(result_filters)
+    _model_query_hooks.setdefault(model, {})[name] = {
+        'query': query_hook,
+        'filter': filter_hook,
+        'result_filters': result_filters
+    }
+
+
+def get_hooks(model):
+    """Retrieve the model query hooks for a model.
+
+    :param model: The DB Model to look up for query hooks.
+    :type model: sqlalchemy orm model
+
+    :return: list of hooks
+    :rtype: list of dict of callable
+
+    """
+    return _model_query_hooks.get(model, {}).values()
diff --git a/neutron/db/_resource_extend.py b/neutron/db/_resource_extend.py
new file mode 100644
index 00000000000..a5456d19129
--- /dev/null
+++ b/neutron/db/_resource_extend.py
@@ -0,0 +1,61 @@
+#    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.
+
+"""
+NOTE: This module shall not be used by external projects. It will be moved
+      to neutron-lib in due course, and then it can be used from there.
+"""
+
+from neutron.common import utils
+
+# This dictionary will store methods for extending API resources.
+# Extensions can add their own methods by invoking register_funcs().
+_resource_extend_functions = {
+    # <resource1> : [<func1>, <func2>, ...],
+    # <resource2> : [<func1>, <func2>, ...],
+    # ...
+}
+
+
+def register_funcs(resource, funcs):
+    """Add functions to extend a resource.
+
+    :param resource: A resource collection name.
+    :type resource: str
+
+    :param funcs: A list of functions.
+    :type funcs: list of callable
+
+    These functions take a resource dict and a resource object and
+    update the resource dict with extension data (possibly retrieved
+    from the resource db object).
+        def _extend_foo_with_bar(foo_res, foo_db):
+            foo_res['bar'] = foo_db.bar_info  # example
+            return foo_res
+
+    """
+    funcs = [utils.make_weak_ref(f) if callable(f) else f
+             for f in funcs]
+    _resource_extend_functions.setdefault(resource, []).extend(funcs)
+
+
+def get_funcs(resource):
+    """Retrieve a list of functions extending a resource.
+
+    :param resource: A resource collection name.
+    :type resource: str
+
+    :return: A list (possibly empty) of functions extending resource.
+    :rtype: list of callable
+
+    """
+    return _resource_extend_functions.get(resource, [])
diff --git a/neutron/db/address_scope_db.py b/neutron/db/address_scope_db.py
index d41bfc18abc..3ff6461a21e 100644
--- a/neutron/db/address_scope_db.py
+++ b/neutron/db/address_scope_db.py
@@ -17,9 +17,9 @@ from oslo_utils import uuidutils
 
 from neutron._i18n import _
 from neutron.api.v2 import attributes as attr
+from neutron.db import _resource_extend as resource_extend
 from neutron.db import _utils as db_utils
 from neutron.db import api as db_api
-from neutron.db import db_base_plugin_v2
 from neutron.extensions import address_scope as ext_address_scope
 from neutron.objects import address_scope as obj_addr_scope
 from neutron.objects import base as base_obj
@@ -133,5 +133,5 @@ class AddressScopeDbMixin(ext_address_scope.AddressScopePluginBase):
                 network_res[ext_address_scope.IPV6_ADDRESS_SCOPE] = as_id
         return network_res
 
-    db_base_plugin_v2.NeutronDbPluginV2.register_dict_extend_funcs(
+    resource_extend.register_funcs(
         attr.NETWORKS, ['_extend_network_dict_address_scope'])
diff --git a/neutron/db/allowedaddresspairs_db.py b/neutron/db/allowedaddresspairs_db.py
index 665a2a88a83..972fc00f8a6 100644
--- a/neutron/db/allowedaddresspairs_db.py
+++ b/neutron/db/allowedaddresspairs_db.py
@@ -16,8 +16,8 @@
 from neutron_lib.api import validators
 
 from neutron.api.v2 import attributes as attr
+from neutron.db import _resource_extend as resource_extend
 from neutron.db import _utils as db_utils
-from neutron.db import db_base_plugin_v2
 
 from neutron.common import utils
 from neutron.extensions import allowedaddresspairs as addr_pair
@@ -73,8 +73,7 @@ class AllowedAddressPairsMixin(object):
         port_res[addr_pair.ADDRESS_PAIRS] = allowed_address_pairs
         return port_res
 
-    # Register dict extend functions for ports
-    db_base_plugin_v2.NeutronDbPluginV2.register_dict_extend_funcs(
+    resource_extend.register_funcs(
         attr.PORTS, ['_extend_port_dict_allowed_address_pairs'])
 
     def _delete_allowed_address_pairs(self, context, id):
diff --git a/neutron/db/availability_zone/network.py b/neutron/db/availability_zone/network.py
index 5b4b98412a5..422ed2ca7b3 100644
--- a/neutron/db/availability_zone/network.py
+++ b/neutron/db/availability_zone/network.py
@@ -12,7 +12,7 @@
 #    under the License.
 
 from neutron.api.v2 import attributes
-from neutron.db import common_db_mixin
+from neutron.db import _resource_extend as resource_extend
 from neutron.extensions import availability_zone as az_ext
 from neutron.extensions import network_availability_zone as net_az
 
@@ -26,5 +26,5 @@ class NetworkAvailabilityZoneMixin(net_az.NetworkAvailabilityZonePluginBase):
         net_res[az_ext.AVAILABILITY_ZONES] = (
             self.get_network_availability_zones(net_db))
 
-    common_db_mixin.CommonDbMixin.register_dict_extend_funcs(
+    resource_extend.register_funcs(
         attributes.NETWORKS, ['_extend_availability_zone'])
diff --git a/neutron/db/common_db_mixin.py b/neutron/db/common_db_mixin.py
index 5402df2a742..439a79dba9a 100644
--- a/neutron/db/common_db_mixin.py
+++ b/neutron/db/common_db_mixin.py
@@ -24,7 +24,8 @@ from sqlalchemy import or_
 from sqlalchemy import sql
 
 from neutron.api.v2 import attributes
-from neutron.common import utils
+from neutron.db import _model_query
+from neutron.db import _resource_extend
 from neutron.db import _utils as ndb_utils
 
 
@@ -37,52 +38,20 @@ resource_fields = ndb_utils.resource_fields
 
 class CommonDbMixin(object):
     """Common methods used in core and service plugins."""
-    # Plugins, mixin classes implementing extension will register
-    # hooks into the dict below for "augmenting" the "core way" of
-    # building a query for retrieving objects from a model class.
-    # To this aim, the register_model_query_hook and unregister_query_hook
-    # from this class should be invoked
-    _model_query_hooks = {}
 
-    # This dictionary will store methods for extending attributes of
-    # api resources. Mixins can use this dict for adding their own methods
-    # TODO(salvatore-orlando): Avoid using class-level variables
-    _dict_extend_functions = {}
-
-    @classmethod
-    def register_model_query_hook(cls, model, name, query_hook, filter_hook,
+    @staticmethod
+    def register_model_query_hook(model, name, query_hook, filter_hook,
                                   result_filters=None):
-        """Register a hook to be invoked when a query is executed.
+        _model_query.register_hook(
+            model, name, query_hook, filter_hook,
+            result_filters=result_filters)
 
-        Add the hooks to the _model_query_hooks dict. Models are the keys
-        of this dict, whereas the value is another dict mapping hook names to
-        callables performing the hook.
-        Each hook has a "query" component, used to build the query expression
-        and a "filter" component, which is used to build the filter expression.
-
-        Query hooks take as input the query being built and return a
-        transformed query expression.
-
-        Filter hooks take as input the filter expression being built and return
-        a transformed filter expression
-        """
-        if callable(query_hook):
-            query_hook = utils.make_weak_ref(query_hook)
-        if callable(filter_hook):
-            filter_hook = utils.make_weak_ref(filter_hook)
-        if callable(result_filters):
-            result_filters = utils.make_weak_ref(result_filters)
-        cls._model_query_hooks.setdefault(model, {})[name] = {
-            'query': query_hook, 'filter': filter_hook,
-            'result_filters': result_filters}
-
-    @classmethod
-    def register_dict_extend_funcs(cls, resource, funcs):
-        funcs = [utils.make_weak_ref(f) if callable(f) else f
-                 for f in funcs]
-        cls._dict_extend_functions.setdefault(resource, []).extend(funcs)
+    @staticmethod
+    def register_dict_extend_funcs(resource, funcs):
+        _resource_extend.register_funcs(resource, funcs)
 
     @property
+    # TODO(HenryG): Remove; used only by vmware-nsx.
     def safe_reference(self):
         """Return a weakref to the instance.
 
@@ -115,13 +84,12 @@ class CommonDbMixin(object):
             else:
                 query_filter = (model.tenant_id == context.tenant_id)
         # Execute query hooks registered from mixins and plugins
-        for _name, hooks in six.iteritems(self._model_query_hooks.get(model,
-                                                                      {})):
-            query_hook = self._resolve_ref(hooks.get('query'))
+        for hook in _model_query.get_hooks(model):
+            query_hook = self._resolve_ref(hook.get('query'))
             if query_hook:
                 query = query_hook(context, model, query)
 
-            filter_hook = self._resolve_ref(hooks.get('filter'))
+            filter_hook = self._resolve_ref(hook.get('filter'))
             if filter_hook:
                 query_filter = filter_hook(context, model, query_filter)
 
@@ -195,10 +163,10 @@ class CommonDbMixin(object):
                         # scoped query
                         query = query.outerjoin(model.rbac_entries)
                     query = query.filter(is_shared)
-            for _nam, hooks in six.iteritems(self._model_query_hooks.get(model,
-                                                                         {})):
+            for hook in _model_query.get_hooks(model):
                 result_filter = self._resolve_ref(
-                    hooks.get('result_filters', None))
+                    hook.get('result_filters', None))
+
                 if result_filter:
                     query = result_filter(query, filters)
         return query
@@ -213,8 +181,7 @@ class CommonDbMixin(object):
 
     def _apply_dict_extend_functions(self, resource_type,
                                      response, db_object):
-        for func in self._dict_extend_functions.get(
-            resource_type, []):
+        for func in _resource_extend.get_funcs(resource_type):
             args = (response, db_object)
             if not isinstance(func, six.string_types):
                 # must call unbound method - use self as 1st argument
diff --git a/neutron/db/db_base_plugin_v2.py b/neutron/db/db_base_plugin_v2.py
index 2d1120b39b9..8d2e16a3084 100644
--- a/neutron/db/db_base_plugin_v2.py
+++ b/neutron/db/db_base_plugin_v2.py
@@ -41,6 +41,7 @@ from neutron.common import constants as n_const
 from neutron.common import exceptions as n_exc
 from neutron.common import ipv6_utils
 from neutron.common import utils
+from neutron.db import _model_query as model_query
 from neutron.db import _utils as ndb_utils
 from neutron.db import api as db_api
 from neutron.db import db_base_plugin_common
@@ -1388,7 +1389,7 @@ class NeutronDbPluginV2(db_base_plugin_common.DbBasePluginCommon,
                 if tenant_id != router['tenant_id']:
                     raise n_exc.DeviceIDNotOwnedByTenant(device_id=device_id)
 
-    db_base_plugin_common.DbBasePluginCommon.register_model_query_hook(
+    model_query.register_hook(
         models_v2.Port,
         "port",
         None,
diff --git a/neutron/db/dns_db.py b/neutron/db/dns_db.py
index c3e5902d4e2..f71d2a4a74c 100644
--- a/neutron/db/dns_db.py
+++ b/neutron/db/dns_db.py
@@ -20,7 +20,7 @@ from oslo_log import log as logging
 
 from neutron._i18n import _, _LE
 from neutron.common import utils
-from neutron.db import db_base_plugin_v2
+from neutron.db import _resource_extend as resource_extend
 from neutron.extensions import dns
 from neutron.extensions import l3
 from neutron.objects import floatingip as fip_obj
@@ -71,8 +71,7 @@ class DNSDbMixin(object):
             floatingip_res['dns_name'] = floatingip_db.dns['dns_name']
         return floatingip_res
 
-    # Register dict extend functions for floating ips
-    db_base_plugin_v2.NeutronDbPluginV2.register_dict_extend_funcs(
+    resource_extend.register_funcs(
         l3.FLOATINGIPS, ['_extend_floatingip_dict_dns'])
 
     def _process_dns_floatingip_create_precommit(self, context,
diff --git a/neutron/db/external_net_db.py b/neutron/db/external_net_db.py
index 985a0a99750..3d1c7a4c0d3 100644
--- a/neutron/db/external_net_db.py
+++ b/neutron/db/external_net_db.py
@@ -25,8 +25,9 @@ from neutron.callbacks import events
 from neutron.callbacks import exceptions as c_exc
 from neutron.callbacks import registry
 from neutron.callbacks import resources
+from neutron.db import _model_query as model_query
+from neutron.db import _resource_extend as resource_extend
 from neutron.db import _utils as db_utils
-from neutron.db import db_base_plugin_v2
 from neutron.db.models import l3 as l3_models
 from neutron.db import models_v2
 from neutron.db import rbac_db_models as rbac_db
@@ -67,10 +68,7 @@ class External_net_db_mixin(object):
             return query.filter(models_v2.Network.external.has())
         return query.filter(~models_v2.Network.external.has())
 
-    # TODO(salvatore-orlando): Perform this operation without explicitly
-    # referring to db_base_plugin_v2, as plugins that do not extend from it
-    # might exist in the future
-    db_base_plugin_v2.NeutronDbPluginV2.register_model_query_hook(
+    model_query.register_hook(
         models_v2.Network,
         "external_net",
         None,
@@ -86,8 +84,7 @@ class External_net_db_mixin(object):
         network_res[external_net.EXTERNAL] = network_db.external is not None
         return network_res
 
-    # Register dict extend functions for networks
-    db_base_plugin_v2.NeutronDbPluginV2.register_dict_extend_funcs(
+    resource_extend.register_funcs(
         attributes.NETWORKS, ['_extend_network_dict_l3'])
 
     def _process_l3_create(self, context, net_data, req_data):
diff --git a/neutron/db/extradhcpopt_db.py b/neutron/db/extradhcpopt_db.py
index 7a78c11c2a6..1184bf30a9a 100644
--- a/neutron/db/extradhcpopt_db.py
+++ b/neutron/db/extradhcpopt_db.py
@@ -14,7 +14,7 @@
 #    under the License.
 
 from neutron.api.v2 import attributes
-from neutron.db import db_base_plugin_v2
+from neutron.db import _resource_extend as resource_extend
 from neutron.extensions import extra_dhcp_opt as edo_ext
 from neutron.objects.port.extensions import extra_dhcp_opt as obj_extra_dhcp
 
@@ -120,5 +120,5 @@ class ExtraDhcpOptMixin(object):
                                       for dho in port.dhcp_opts]
         return res
 
-    db_base_plugin_v2.NeutronDbPluginV2.register_dict_extend_funcs(
+    resource_extend.register_funcs(
         attributes.PORTS, ['_extend_port_dict_extra_dhcp_opt'])
diff --git a/neutron/db/extraroute_db.py b/neutron/db/extraroute_db.py
index 3a3bc621483..02ba7e01166 100644
--- a/neutron/db/extraroute_db.py
+++ b/neutron/db/extraroute_db.py
@@ -20,7 +20,7 @@ from oslo_log import log as logging
 
 from neutron._i18n import _
 from neutron.common import utils
-from neutron.db import db_base_plugin_v2
+from neutron.db import _resource_extend as resource_extend
 from neutron.db import l3_db
 from neutron.db import models_v2
 from neutron.extensions import extraroute
@@ -48,7 +48,7 @@ class ExtraRoute_dbonly_mixin(l3_db.L3_NAT_dbonly_mixin):
                                     router_db['route_list']
                                 ))
 
-    db_base_plugin_v2.NeutronDbPluginV2.register_dict_extend_funcs(
+    resource_extend.register_funcs(
         l3.ROUTERS, ['_extend_router_dict_extraroute'])
 
     def update_router(self, context, id, router):
diff --git a/neutron/db/l3_attrs_db.py b/neutron/db/l3_attrs_db.py
index bd868b659d3..5d8b0efa92a 100644
--- a/neutron/db/l3_attrs_db.py
+++ b/neutron/db/l3_attrs_db.py
@@ -15,7 +15,7 @@
 from oslo_config import cfg
 
 from neutron._i18n import _
-from neutron.db import db_base_plugin_v2
+from neutron.db import _resource_extend as resource_extend
 from neutron.db.models import l3_attrs
 from neutron.extensions import availability_zone as az
 from neutron.extensions import l3
@@ -62,5 +62,5 @@ class ExtraAttributesMixin(object):
             raise RuntimeError(_("Tried to set a key '%s' that doesn't exist "
                                  "in the extra attributes table.") % key)
 
-    db_base_plugin_v2.NeutronDbPluginV2.register_dict_extend_funcs(
+    resource_extend.register_funcs(
         l3.ROUTERS, ['_extend_extra_router_dict'])
diff --git a/neutron/db/l3_gwmode_db.py b/neutron/db/l3_gwmode_db.py
index ec7c7b4b48c..ff44c29e424 100644
--- a/neutron/db/l3_gwmode_db.py
+++ b/neutron/db/l3_gwmode_db.py
@@ -18,7 +18,7 @@ import sqlalchemy as sa
 from sqlalchemy import sql
 
 from neutron._i18n import _
-from neutron.db import db_base_plugin_v2
+from neutron.db import _resource_extend as resource_extend
 from neutron.db import l3_db
 from neutron.db.models import l3 as l3_models
 from neutron.extensions import l3
@@ -41,8 +41,7 @@ setattr(l3_models.Router, 'enable_snat',
 class L3_NAT_dbonly_mixin(l3_db.L3_NAT_dbonly_mixin):
     """Mixin class to add configurable gateway modes."""
 
-    # Register dict extend functions for ports and networks
-    db_base_plugin_v2.NeutronDbPluginV2.register_dict_extend_funcs(
+    resource_extend.register_funcs(
         l3.ROUTERS, ['_extend_router_dict_gw_mode'])
 
     def _extend_router_dict_gw_mode(self, router_res, router_db):
diff --git a/neutron/db/netmtu_db.py b/neutron/db/netmtu_db.py
index 101477a4966..1f983b8941c 100644
--- a/neutron/db/netmtu_db.py
+++ b/neutron/db/netmtu_db.py
@@ -16,7 +16,7 @@
 from oslo_config import cfg
 
 from neutron.api.v2 import attributes
-from neutron.db import db_base_plugin_v2
+from neutron.db import _resource_extend as resource_extend
 from neutron.extensions import netmtu
 from neutron.plugins.common import utils
 
@@ -36,5 +36,5 @@ class Netmtu_db_mixin(object):
         network_res[netmtu.MTU] = utils.get_deployment_physnet_mtu()
         return network_res
 
-    db_base_plugin_v2.NeutronDbPluginV2.register_dict_extend_funcs(
+    resource_extend.register_funcs(
         attributes.NETWORKS, ['_extend_network_dict_mtu'])
diff --git a/neutron/db/portbindings_base.py b/neutron/db/portbindings_base.py
index 8114d2c529f..c9b51a7fc96 100644
--- a/neutron/db/portbindings_base.py
+++ b/neutron/db/portbindings_base.py
@@ -14,7 +14,7 @@
 #    under the License.
 
 from neutron.api.v2 import attributes
-from neutron.db import db_base_plugin_v2
+from neutron.db import _resource_extend as resource_extend
 
 
 class PortBindingBaseMixin(object):
@@ -36,5 +36,5 @@ def _extend_port_dict_binding(plugin, port_res, port_db):
 
 
 def register_port_dict_function():
-    db_base_plugin_v2.NeutronDbPluginV2.register_dict_extend_funcs(
+    resource_extend.register_funcs(
         attributes.PORTS, [_extend_port_dict_binding])
diff --git a/neutron/db/portbindings_db.py b/neutron/db/portbindings_db.py
index 9cd8b076e9b..fe79d4b297e 100644
--- a/neutron/db/portbindings_db.py
+++ b/neutron/db/portbindings_db.py
@@ -16,7 +16,8 @@
 from neutron_lib.api import validators
 
 from neutron.api.v2 import attributes
-from neutron.db import db_base_plugin_v2
+from neutron.db import _model_query as model_query
+from neutron.db import _resource_extend as resource_extend
 from neutron.db.models import portbinding as pmodels
 from neutron.db import models_v2
 from neutron.db import portbindings_base
@@ -39,7 +40,7 @@ class PortBindingMixin(portbindings_base.PortBindingBaseMixin):
         query = query.filter(pmodels.PortBindingPort.host.in_(values))
         return query
 
-    db_base_plugin_v2.NeutronDbPluginV2.register_model_query_hook(
+    model_query.register_hook(
         models_v2.Port,
         "portbindings_port",
         '_port_model_hook',
@@ -102,6 +103,4 @@ def _extend_port_dict_binding(plugin, port_res, port_db):
     plugin.extend_port_dict_binding(port_res, port_db)
 
 
-# Register dict extend functions for ports
-db_base_plugin_v2.NeutronDbPluginV2.register_dict_extend_funcs(
-    attributes.PORTS, [_extend_port_dict_binding])
+resource_extend.register_funcs(attributes.PORTS, [_extend_port_dict_binding])
diff --git a/neutron/db/portsecurity_db.py b/neutron/db/portsecurity_db.py
index 70d177c4ff3..bd551270bbf 100644
--- a/neutron/db/portsecurity_db.py
+++ b/neutron/db/portsecurity_db.py
@@ -16,16 +16,15 @@ from neutron_lib.api import validators
 
 from neutron.api.v2 import attributes as attrs
 from neutron.common import utils
-from neutron.db import db_base_plugin_v2
+from neutron.db import _resource_extend as resource_extend
 from neutron.db import portsecurity_db_common
 from neutron.extensions import portsecurity as psec
 
 
 class PortSecurityDbMixin(portsecurity_db_common.PortSecurityDbCommon):
-    # Register dict extend functions for ports and networks
-    db_base_plugin_v2.NeutronDbPluginV2.register_dict_extend_funcs(
+    resource_extend.register_funcs(
         attrs.NETWORKS, ['_extend_port_security_dict'])
-    db_base_plugin_v2.NeutronDbPluginV2.register_dict_extend_funcs(
+    resource_extend.register_funcs(
         attrs.PORTS, ['_extend_port_security_dict'])
 
     def _extend_port_security_dict(self, response_data, db_data):
diff --git a/neutron/db/securitygroups_db.py b/neutron/db/securitygroups_db.py
index 6f71dfa4ee7..96379b2ff14 100644
--- a/neutron/db/securitygroups_db.py
+++ b/neutron/db/securitygroups_db.py
@@ -28,9 +28,9 @@ from neutron.callbacks import registry
 from neutron.callbacks import resources
 from neutron.common import constants as n_const
 from neutron.common import utils
+from neutron.db import _resource_extend as resource_extend
 from neutron.db import _utils as db_utils
 from neutron.db import api as db_api
-from neutron.db import db_base_plugin_v2
 from neutron.db.models import securitygroup as sg_models
 from neutron.extensions import securitygroup as ext_sg
 
@@ -662,8 +662,7 @@ class SecurityGroupDbMixin(ext_sg.SecurityGroupPluginBase):
         port_res[ext_sg.SECURITYGROUPS] = security_group_ids
         return port_res
 
-    # Register dict extend functions for ports
-    db_base_plugin_v2.NeutronDbPluginV2.register_dict_extend_funcs(
+    resource_extend.register_funcs(
         attributes.PORTS, ['_extend_port_dict_security_group'])
 
     def _process_port_create_security_group(self, context, port,
diff --git a/neutron/db/standardattrdescription_db.py b/neutron/db/standardattrdescription_db.py
index ec566bd37b5..98548ece5b4 100644
--- a/neutron/db/standardattrdescription_db.py
+++ b/neutron/db/standardattrdescription_db.py
@@ -12,7 +12,7 @@
 #    License for the specific language governing permissions and limitations
 #    under the License.
 
-from neutron.db import common_db_mixin
+from neutron.db import _resource_extend as resource_extend
 from neutron.db import standard_attr
 
 
@@ -26,7 +26,7 @@ class StandardAttrDescriptionMixin(object):
 
     def __new__(cls, *args, **kwargs):
         for resource in standard_attr.get_standard_attr_resource_model_map():
-            common_db_mixin.CommonDbMixin.register_dict_extend_funcs(
+            resource_extend.register_funcs(
                 resource, ['_extend_standard_attr_description'])
         return super(StandardAttrDescriptionMixin, cls).__new__(cls, *args,
                                                                 **kwargs)
diff --git a/neutron/db/subnet_service_type_db_models.py b/neutron/db/subnet_service_type_db_models.py
index 115ac4ac34b..60f2be95a69 100644
--- a/neutron/db/subnet_service_type_db_models.py
+++ b/neutron/db/subnet_service_type_db_models.py
@@ -17,7 +17,7 @@
 # any models at all
 
 from neutron.api.v2 import attributes
-from neutron.db import common_db_mixin
+from neutron.db import _resource_extend as resource_extend
 
 
 class SubnetServiceTypeMixin(object):
@@ -28,5 +28,5 @@ class SubnetServiceTypeMixin(object):
                                        service_type in
                                        subnet_db.service_types]
 
-    common_db_mixin.CommonDbMixin.register_dict_extend_funcs(
+    resource_extend.register_funcs(
         attributes.SUBNETS, [_extend_subnet_service_types])
diff --git a/neutron/db/vlantransparent_db.py b/neutron/db/vlantransparent_db.py
index ba024fe6b17..1af6ad4bbf1 100644
--- a/neutron/db/vlantransparent_db.py
+++ b/neutron/db/vlantransparent_db.py
@@ -13,7 +13,7 @@
 #    under the License.
 
 from neutron.api.v2 import attributes
-from neutron.db import db_base_plugin_v2
+from neutron.db import _resource_extend as resource_extend
 from neutron.extensions import vlantransparent
 
 
@@ -25,5 +25,5 @@ class Vlantransparent_db_mixin(object):
             network_db.vlan_transparent)
         return network_res
 
-    db_base_plugin_v2.NeutronDbPluginV2.register_dict_extend_funcs(
+    resource_extend.register_funcs(
         attributes.NETWORKS, ['_extend_network_dict_vlan_transparent'])
diff --git a/neutron/plugins/ml2/plugin.py b/neutron/plugins/ml2/plugin.py
index 9173725ac9a..f59bcdc4ade 100644
--- a/neutron/plugins/ml2/plugin.py
+++ b/neutron/plugins/ml2/plugin.py
@@ -46,6 +46,8 @@ from neutron.common import constants as n_const
 from neutron.common import rpc as n_rpc
 from neutron.common import topics
 from neutron.common import utils
+from neutron.db import _model_query as model_query
+from neutron.db import _resource_extend as resource_extend
 from neutron.db import _utils as db_utils
 from neutron.db import address_scope_db
 from neutron.db import agents_db
@@ -579,17 +581,16 @@ class Ml2Plugin(db_base_plugin_v2.NeutronDbPluginV2,
         if port_db.port_binding:
             self._update_port_dict_binding(port_res, port_db.port_binding)
 
-    db_base_plugin_v2.NeutronDbPluginV2.register_dict_extend_funcs(
+    resource_extend.register_funcs(
         attributes.PORTS, ['_ml2_extend_port_dict_binding'])
 
-    # Register extend dict methods for network and port resources.
-    # Each mechanism driver that supports extend attribute for the resources
-    # can add those attribute to the result.
-    db_base_plugin_v2.NeutronDbPluginV2.register_dict_extend_funcs(
+    # ML2's resource extend functions allow extension drivers that extend
+    # attributes for the resources to add those attributes to the result.
+    resource_extend.register_funcs(
                attributes.NETWORKS, ['_ml2_md_extend_network_dict'])
-    db_base_plugin_v2.NeutronDbPluginV2.register_dict_extend_funcs(
+    resource_extend.register_funcs(
                attributes.PORTS, ['_ml2_md_extend_port_dict'])
-    db_base_plugin_v2.NeutronDbPluginV2.register_dict_extend_funcs(
+    resource_extend.register_funcs(
                attributes.SUBNETS, ['_ml2_md_extend_subnet_dict'])
 
     def _ml2_md_extend_network_dict(self, result, netdb):
@@ -616,7 +617,7 @@ class Ml2Plugin(db_base_plugin_v2.NeutronDbPluginV2,
         bind_criteria = models.PortBinding.host.in_(values)
         return query.filter(models_v2.Port.port_binding.has(bind_criteria))
 
-    db_base_plugin_v2.NeutronDbPluginV2.register_model_query_hook(
+    model_query.register_hook(
         models_v2.Port,
         "ml2_port_bindings",
         None,
diff --git a/neutron/services/auto_allocate/db.py b/neutron/services/auto_allocate/db.py
index e450ffab0b9..2ff29a9b501 100644
--- a/neutron/services/auto_allocate/db.py
+++ b/neutron/services/auto_allocate/db.py
@@ -25,10 +25,10 @@ from neutron.callbacks import events
 from neutron.callbacks import registry
 from neutron.callbacks import resources
 from neutron.common import exceptions as c_exc
+from neutron.db import _resource_extend as resource_extend
 from neutron.db import _utils as db_utils
 from neutron.db import api as db_api
 from neutron.db import common_db_mixin
-from neutron.db import db_base_plugin_v2
 from neutron.extensions import l3
 from neutron.objects import auto_allocate as auto_allocate_obj
 from neutron.objects import base as base_obj
@@ -75,7 +75,7 @@ def _ensure_external_network_default_value_callback(
 
 class AutoAllocatedTopologyMixin(common_db_mixin.CommonDbMixin):
 
-    db_base_plugin_v2.NeutronDbPluginV2.register_dict_extend_funcs(
+    resource_extend.register_funcs(
         attributes.NETWORKS, [_extend_external_network_default])
 
     def __new__(cls, *args, **kwargs):
diff --git a/neutron/services/l3_router/l3_router_plugin.py b/neutron/services/l3_router/l3_router_plugin.py
index 9ed3ee9ec81..6e521816a20 100644
--- a/neutron/services/l3_router/l3_router_plugin.py
+++ b/neutron/services/l3_router/l3_router_plugin.py
@@ -22,6 +22,7 @@ from neutron.api.rpc.agentnotifiers import l3_rpc_agent_api
 from neutron.api.rpc.handlers import l3_rpc
 from neutron.common import rpc as n_rpc
 from neutron.common import topics
+from neutron.db import _resource_extend as resource_extend
 from neutron.db import common_db_mixin
 from neutron.db import dns_db
 from neutron.db import extraroute_db
@@ -125,5 +126,5 @@ def add_flavor_id(plugin, router_res, router_db):
     router_res['flavor_id'] = router_db['flavor_id']
 
 
-common_db_mixin.CommonDbMixin.register_dict_extend_funcs(
+resource_extend.register_funcs(
     l3.ROUTERS, [add_flavor_id])
diff --git a/neutron/services/revisions/revision_plugin.py b/neutron/services/revisions/revision_plugin.py
index ab32b131c0a..853704e4242 100644
--- a/neutron/services/revisions/revision_plugin.py
+++ b/neutron/services/revisions/revision_plugin.py
@@ -17,8 +17,8 @@ from sqlalchemy.orm import exc
 from sqlalchemy.orm import session as se
 
 from neutron._i18n import _, _LW
+from neutron.db import _resource_extend as resource_extend
 from neutron.db import api as db_api
-from neutron.db import db_base_plugin_v2
 from neutron.db import standard_attr
 from neutron.services import service_base
 
@@ -33,7 +33,7 @@ class RevisionPlugin(service_base.ServicePluginBase):
     def __init__(self):
         super(RevisionPlugin, self).__init__()
         for resource in standard_attr.get_standard_attr_resource_model_map():
-            db_base_plugin_v2.NeutronDbPluginV2.register_dict_extend_funcs(
+            resource_extend.register_funcs(
                 resource, [self.extend_resource_dict_revision])
         db_api.sqla_listen(se.Session, 'before_flush', self.bump_revisions)
 
diff --git a/neutron/services/segments/plugin.py b/neutron/services/segments/plugin.py
index 1cde18056a7..602124f7f70 100644
--- a/neutron/services/segments/plugin.py
+++ b/neutron/services/segments/plugin.py
@@ -29,7 +29,7 @@ from neutron.callbacks import events
 from neutron.callbacks import registry
 from neutron.callbacks import resources
 from neutron.common import exceptions as n_exc
-from neutron.db import common_db_mixin
+from neutron.db import _resource_extend as resource_extend
 from neutron.db.models import segment as segment_model
 from neutron.db import models_v2
 from neutron.extensions import ip_allocation
@@ -79,11 +79,11 @@ class Plugin(db.SegmentDbMixin, segment.SegmentPluginBase):
     supported_extension_aliases = ["segment", "ip_allocation", "l2_adjacency"]
 
     def __init__(self):
-        common_db_mixin.CommonDbMixin.register_dict_extend_funcs(
+        resource_extend.register_funcs(
             attributes.NETWORKS, [_extend_network_dict_binding])
-        common_db_mixin.CommonDbMixin.register_dict_extend_funcs(
+        resource_extend.register_funcs(
             attributes.SUBNETS, [_extend_subnet_dict_binding])
-        common_db_mixin.CommonDbMixin.register_dict_extend_funcs(
+        resource_extend.register_funcs(
             attributes.PORTS, [_extend_port_dict_binding])
         self.nova_updater = NovaSegmentNotifier()
 
diff --git a/neutron/services/tag/tag_plugin.py b/neutron/services/tag/tag_plugin.py
index 5dbc76dc17f..3285c617187 100644
--- a/neutron/services/tag/tag_plugin.py
+++ b/neutron/services/tag/tag_plugin.py
@@ -21,6 +21,8 @@ from oslo_log import helpers as log_helpers
 from sqlalchemy.orm import exc
 
 from neutron.api.v2 import attributes
+from neutron.db import _model_query as model_query
+from neutron.db import _resource_extend as resource_extend
 from neutron.db import api as db_api
 from neutron.db import common_db_mixin
 from neutron.db.models import l3 as l3_model
@@ -31,6 +33,7 @@ from neutron.extensions import l3 as l3_ext
 from neutron.extensions import tag as tag_ext
 
 
+# Taggable resources
 resource_model_map = {
     # When we'll add other resources, we must add new extension for them
     # if we don't have better discovery mechanism instead of it.
@@ -131,13 +134,11 @@ class TagPlugin(common_db_mixin.CommonDbMixin, tag_ext.TagPluginBase):
     def __new__(cls, *args, **kwargs):
         inst = super(TagPlugin, cls).__new__(cls, *args, **kwargs)
         inst._filter_methods = []  # prevent GC of our partial functions
-        # support only _apply_dict_extend_functions supported resources
-        # at the moment.
         for resource, model in resource_model_map.items():
-            common_db_mixin.CommonDbMixin.register_dict_extend_funcs(
+            resource_extend.register_funcs(
                 resource, [_extend_tags_dict])
             method = functools.partial(tag_methods.apply_tag_filters, model)
             inst._filter_methods.append(method)
-            common_db_mixin.CommonDbMixin.register_model_query_hook(
+            model_query.register_hook(
                 model, "tag", None, None, method)
         return inst
diff --git a/neutron/services/timestamp/timestamp_plugin.py b/neutron/services/timestamp/timestamp_plugin.py
index eee6aadeeb4..a1926ac0e82 100644
--- a/neutron/services/timestamp/timestamp_plugin.py
+++ b/neutron/services/timestamp/timestamp_plugin.py
@@ -12,7 +12,8 @@
 #    License for the specific language governing permissions and limitations
 #    under the License.
 
-from neutron.db import db_base_plugin_v2
+from neutron.db import _model_query as model_query
+from neutron.db import _resource_extend as resource_extend
 from neutron.db import models_v2
 from neutron.db import standard_attr
 from neutron.objects import base as base_obj
@@ -31,9 +32,9 @@ class TimeStampPlugin(service_base.ServicePluginBase,
         self.register_db_events()
         rs_model_maps = standard_attr.get_standard_attr_resource_model_map()
         for rsmap, model in rs_model_maps.items():
-            db_base_plugin_v2.NeutronDbPluginV2.register_dict_extend_funcs(
+            resource_extend.register_funcs(
                 rsmap, [self.extend_resource_dict_timestamp])
-            db_base_plugin_v2.NeutronDbPluginV2.register_model_query_hook(
+            model_query.register_hook(
                 model, "change_since_query", None, None,
                 self._change_since_result_filter_hook)
         # TODO(jlibosva): Move this to register_model_query_hook
diff --git a/neutron/services/trunk/plugin.py b/neutron/services/trunk/plugin.py
index 924785cf1e6..0315e801ce3 100644
--- a/neutron/services/trunk/plugin.py
+++ b/neutron/services/trunk/plugin.py
@@ -22,10 +22,10 @@ from neutron.api.v2 import attributes
 from neutron.callbacks import events
 from neutron.callbacks import registry
 from neutron.callbacks import resources
+from neutron.db import _resource_extend as resource_extend
 from neutron.db import api as db_api
 from neutron.db import common_db_mixin
 from neutron.db import db_base_plugin_common
-from neutron.db import db_base_plugin_v2
 from neutron.extensions import portbindings
 from neutron.objects import base as objects_base
 from neutron.objects import trunk as trunk_objects
@@ -69,7 +69,7 @@ class TrunkPlugin(service_base.ServicePluginBase,
     __native_sorting_support = True
 
     def __init__(self):
-        db_base_plugin_v2.NeutronDbPluginV2.register_dict_extend_funcs(
+        resource_extend.register_funcs(
             attributes.PORTS, [_extend_port_trunk_details])
         self._rpc_backend = None
         self._drivers = []
diff --git a/neutron/tests/tools.py b/neutron/tests/tools.py
index 952a792213a..a778707f7c0 100644
--- a/neutron/tests/tools.py
+++ b/neutron/tests/tools.py
@@ -35,7 +35,7 @@ import unittest2
 
 from neutron.api.v2 import attributes
 from neutron.common import constants as n_const
-from neutron.db import common_db_mixin
+from neutron.db import _model_query as model_query
 from neutron.plugins.common import constants as p_const
 
 
@@ -125,13 +125,13 @@ class SafeCleanupFixture(fixtures.Fixture):
 
 class CommonDbMixinHooksFixture(fixtures.Fixture):
     def _setUp(self):
-        self.original_hooks = common_db_mixin.CommonDbMixin._model_query_hooks
+        self.original_hooks = model_query._model_query_hooks
         self.addCleanup(self.restore_hooks)
-        common_db_mixin.CommonDbMixin._model_query_hooks = copy.copy(
-            common_db_mixin.CommonDbMixin._model_query_hooks)
+        model_query._model_query_hooks = copy.copy(
+            model_query._model_query_hooks)
 
     def restore_hooks(self):
-        common_db_mixin.CommonDbMixin._model_query_hooks = self.original_hooks
+        model_query._model_query_hooks = self.original_hooks
 
 
 def setup_mock_calls(mocked_call, expected_calls_and_values):
diff --git a/neutron/tests/unit/extensions/test_l3.py b/neutron/tests/unit/extensions/test_l3.py
index 373eeebc7d8..c0f4973af11 100644
--- a/neutron/tests/unit/extensions/test_l3.py
+++ b/neutron/tests/unit/extensions/test_l3.py
@@ -37,6 +37,7 @@ from neutron.callbacks import events
 from neutron.callbacks import exceptions
 from neutron.callbacks import registry
 from neutron.callbacks import resources
+from neutron.db import _resource_extend as resource_extend
 from neutron.db import common_db_mixin
 from neutron.db import db_base_plugin_v2
 from neutron.db import dns_db
@@ -616,7 +617,7 @@ class L3NatTestCaseBase(L3NatTestCaseMixin):
         def _extend_router_dict_test_attr(*args, **kwargs):
             self.extension_called = True
 
-        db_base_plugin_v2.NeutronDbPluginV2.register_dict_extend_funcs(
+        resource_extend.register_funcs(
             l3.ROUTERS, [_extend_router_dict_test_attr])
         self.assertFalse(self.extension_called)
         with self.router():
diff --git a/neutron/tests/unit/objects/test_base.py b/neutron/tests/unit/objects/test_base.py
index f7820c7442e..e00949d27e0 100644
--- a/neutron/tests/unit/objects/test_base.py
+++ b/neutron/tests/unit/objects/test_base.py
@@ -31,7 +31,7 @@ import testtools
 
 from neutron.common import constants
 from neutron.common import utils
-from neutron.db import db_base_plugin_v2
+from neutron.db import _model_query as model_query
 from neutron.db.models import l3 as l3_model
 from neutron.db import standard_attr
 from neutron import objects
@@ -1507,7 +1507,7 @@ class BaseDbObjectTestCase(_BaseObjectTestCase,
             return query
 
         self.obj_registry.register(self._test_class)
-        db_base_plugin_v2.NeutronDbPluginV2.register_model_query_hook(
+        model_query.register_hook(
             self._test_class.db_model,
             'foo_filter',
             None,