Create an index for "ports.network_id"

The method ``_port_filter_hook``, that is added in any "Port" SELECT
command, filters the database "Port" registers by "network_id", using
an exact match. This query speed will improve if this column is
indexed in the database engine.

Closes-Bug: #1973349
Change-Id: Ia20f96dc78ea04bb0ab4665e6d47a6365789d2c9

neutron/db/migration/alembic_migrations/versions/EXPAND_HEAD

@@ -1 +1 @@
-I43e0b669096
+4e6e655746f6

neutron/db/migration/alembic_migrations/versions/zed/expand/4e6e655746f6_add_index_to_ports_network_id.py

@@ -0,0 +1,34 @@
+# Copyright 2022 OpenStack Foundation
+#
+#    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.
+#
+
+from alembic import op
+
+
+"""add index to ports.network_id
+
+Revision ID: 4e6e655746f6
+Revises: I43e0b669096
+Create Date: 2022-05-12 13:04:51.831792
+
+"""
+
+# revision identifiers, used by Alembic.
+revision = '4e6e655746f6'
+down_revision = 'I43e0b669096'
+
+
+def upgrade():
+    index_name = 'ix_ports_network_id'
+    op.create_index(index_name, 'ports', ['network_id'], unique=False)

neutron/db/models_v2.py

@@ -106,7 +106,7 @@ class Port(standard_attr.HasStandardAttributes, model_base.BASEV2,
 
     name = sa.Column(sa.String(db_const.NAME_FIELD_SIZE))
     network_id = sa.Column(sa.String(36), sa.ForeignKey("networks.id"),
-                           nullable=False)
+                           nullable=False, index=True)
     fixed_ips = orm.relationship(IPAllocation,
                                  backref=orm.backref('port',
                                                      load_on_pending=True),