Add unique constraints to Cell.

In documentation: "name: Name of the current cell. This must be
unique for each cell"
Added unique constraint 'uniq_cell_name0deleted' ('name','deleted')
to Cell model and migrate sripts.
Added new exception `CellsExists`. Updated cell_create() in db.api.
Tests updated respectively.

blueprint db-enforce-unique-keys

Change-Id: Ib76e167089cb4756e4438613b49013ebf0874afe

3 files changed, 48 insertions, 1 deletions

diff --git a/nova/db/sqlalchemy/api.py b/nova/db/sqlalchemy/api.py
index 664425441..55ef03006 100644
--- a/nova/db/sqlalchemy/api.py
+++ b/nova/db/sqlalchemy/api.py
@@ -4048,7 +4048,10 @@ def instance_type_extra_specs_update_or_create(context, flavor_id, specs):
 def cell_create(context, values):
     cell = models.Cell()
     cell.update(values)
-    cell.save()
+    try:
+        cell.save()
+    except db_exc.DBDuplicateEntry:
+        raise exception.CellExists(name=values['name'])
     return cell
 
 
diff --git a/nova/db/sqlalchemy/migrate_repo/versions/189_add_cells_uc.py b/nova/db/sqlalchemy/migrate_repo/versions/189_add_cells_uc.py
new file mode 100644
index 000000000..d0606e9f9
--- /dev/null
+++ b/nova/db/sqlalchemy/migrate_repo/versions/189_add_cells_uc.py
@@ -0,0 +1,40 @@
+# Copyright 2013 Mirantis Inc.
+# All Rights Reserved
+#
+#    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.
+#
+# vim: tabstop=4 shiftwidth=4 softtabstop=4
+
+from migrate.changeset import UniqueConstraint
+from sqlalchemy import MetaData, Table
+
+from nova.db.sqlalchemy import utils
+
+
+UC_NAME = 'uniq_cell_name0deleted'
+COLUMNS = ('name', 'deleted')
+TABLE_NAME = 'cells'
+
+
+def upgrade(migrate_engine):
+    meta = MetaData(bind=migrate_engine)
+    t = Table(TABLE_NAME, meta, autoload=True)
+
+    utils.drop_old_duplicate_entries_from_table(migrate_engine, TABLE_NAME,
+                                                True, *COLUMNS)
+    uc = UniqueConstraint(*COLUMNS, table=t, name=UC_NAME)
+    uc.create()
+
+
+def downgrade(migrate_engine):
+    utils.drop_unique_constraint(migrate_engine, TABLE_NAME, UC_NAME, *COLUMNS)
diff --git a/nova/db/sqlalchemy/models.py b/nova/db/sqlalchemy/models.py
index 815041638..9b6d849d3 100644
--- a/nova/db/sqlalchemy/models.py
+++ b/nova/db/sqlalchemy/models.py
@@ -859,6 +859,10 @@ class Cell(BASE, NovaBase):
     of entries with is_parent=True or False
     """
     __tablename__ = 'cells'
+    __table_args__ = (schema.UniqueConstraint(
+        "name", "deleted", name="uniq_cell_name0deleted"
+        ),
+    )
     id = Column(Integer, primary_key=True)
     # Name here is the 'short name' of a cell.  For instance: 'child1'
     name = Column(String(255))