Make request_spec.spec MediumText

request_spec.instance_group.members is a list of instance UUIDs. It
can get so long that it overflows its TEXT column. This patch changes
request_spec.spec to MEDIUMTEXT.

Change-Id: I6bf0fa19b72887803e77b66698587c2108c9372a
Closes-bug: 1738094

nova/db/sqlalchemy/api_migrations/migrate_repo/versions/052_request_specs_spec_mediumtext.py

@@ -0,0 +1,25 @@
+#    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 sqlalchemy import MetaData
+from sqlalchemy import Table
+
+from nova.db.sqlalchemy import api_models
+
+
+def upgrade(migrate_engine):
+    meta = MetaData()
+    meta.bind = migrate_engine
+
+    request_specs = Table('request_specs', meta, autoload=True)
+    if request_specs.c.spec.type != api_models.MediumText():
+        request_specs.c.spec.alter(type=api_models.MediumText())

nova/db/sqlalchemy/api_models.py

@@ -168,7 +168,7 @@ class RequestSpec(API_BASE):
 
     id = Column(Integer, primary_key=True)
     instance_uuid = Column(String(36), nullable=False)
-    spec = Column(Text, nullable=False)
+    spec = Column(MediumText(), nullable=False)
 
 
 class Flavors(API_BASE):