Change db deleted column type utils

Move and refactor methods from 152_migration that allows us to change
type of deleted column to type of id.

There are 2 methods:

utils.change_deleted_column_type_to_id_type() method
This method change type of `deleted` column from Boolean to
type of `id`. This method allows us to do it in generic way
for all backends. It fix problem with sqlite, that doesn't
allow any operation with columns that have CheckConstraints.
And columns with Boolean type have CheckConstraints
(value in (0, 1)). So for sqlite it works through shadow tables.
For others dbs it works though alter table.

utils.change_deleted_column_type_to_boolean_type() methods
This method allows us to revert result of previous method.
Useful for downgrade.

In global these methods could be very useful in olso for other
projects. This is a first step that allows us to create unique
constraints when we are using soft delete.
(Create UC on (column, deleted))

Also it will be useful in nova to remove copy past from 179
migration. Add new migration that will fix also shadow_cells table.
And also there are baremetal tables that should be also migrated.

blueprint db-common-migration-and-utils

Change-Id: Ie14351c52eb50182e6460c97e257395ce2adb8b0

nova/tests/test_migration_utils.py

@@ -16,12 +16,14 @@
 #    under the License.
 
 from migrate.changeset import UniqueConstraint
-from sqlalchemy import Integer, DateTime, String
+from sqlalchemy.dialects import mysql
+from sqlalchemy import Boolean, Index, Integer, DateTime, String
 from sqlalchemy import MetaData, Table, Column
+from sqlalchemy.engine import reflection
 from sqlalchemy.exc import NoSuchTableError
 from sqlalchemy.exc import SAWarning
 from sqlalchemy.sql import select
-from sqlalchemy.types import UserDefinedType
+from sqlalchemy.types import UserDefinedType, NullType
 
 from nova.db.sqlalchemy import api as db
 from nova.db.sqlalchemy import utils
@@ -385,3 +387,130 @@ class TestMigrationUtils(test_migrations.BaseMigrationTestCase):
             self.assertRaises(exception.ShadowTableExists,
                               utils.create_shadow_table,
                               engine, table_name=table_name)
+
+    def test_change_deleted_column_type_doesnt_drop_index(self):
+        table_name = 'abc'
+        for key, engine in self.engines.items():
+            meta = MetaData(bind=engine)
+
+            indexes = {
+                'idx_a_deleted': ['a', 'deleted'],
+                'idx_b_deleted': ['b', 'deleted'],
+                'idx_a': ['a']
+            }
+
+            index_instances = [Index(name, *columns)
+                                    for name, columns in indexes.iteritems()]
+
+            table = Table(table_name, meta,
+                          Column('id', Integer, primary_key=True),
+                          Column('a', String(255)),
+                          Column('b', String(255)),
+                          Column('deleted', Boolean),
+                          *index_instances)
+            table.create()
+            utils.change_deleted_column_type_to_id_type(engine, table_name)
+            utils.change_deleted_column_type_to_boolean(engine, table_name)
+
+            insp = reflection.Inspector.from_engine(engine)
+            real_indexes = insp.get_indexes(table_name)
+            self.assertEqual(len(real_indexes), 3)
+            for index in real_indexes:
+                name = index['name']
+                self.assertIn(name, indexes)
+                self.assertEqual(set(index['column_names']),
+                                 set(indexes[name]))
+
+    def test_change_deleted_column_type_to_id_type_integer(self):
+        table_name = 'abc'
+        for key, engine in self.engines.items():
+            meta = MetaData()
+            meta.bind = engine
+            table = Table(table_name, meta,
+                          Column('id', Integer, primary_key=True),
+                          Column('deleted', Boolean))
+            table.create()
+            utils.change_deleted_column_type_to_id_type(engine, table_name)
+
+            table = utils.get_table(engine, table_name)
+            self.assertTrue(isinstance(table.c.deleted.type, Integer))
+
+    def test_change_deleted_column_type_to_id_type_string(self):
+        table_name = 'abc'
+        for key, engine in self.engines.items():
+            meta = MetaData()
+            meta.bind = engine
+            table = Table(table_name, meta,
+                          Column('id', String(255), primary_key=True),
+                          Column('deleted', Boolean))
+            table.create()
+            utils.change_deleted_column_type_to_id_type(engine, table_name)
+
+            table = utils.get_table(engine, table_name)
+            self.assertTrue(isinstance(table.c.deleted.type, String))
+
+    def test_change_deleted_column_type_to_id_type_custom(self):
+        table_name = 'abc'
+        engine = self.engines['sqlite']
+        meta = MetaData()
+        meta.bind = engine
+        table = Table(table_name, meta,
+                      Column('id', Integer, primary_key=True),
+                      Column('foo', CustomType),
+                      Column('deleted', Boolean))
+        table.create()
+
+        self.assertRaises(exception.NovaException,
+                          utils.change_deleted_column_type_to_id_type,
+                          engine, table_name)
+
+        fooColumn = Column('foo', CustomType())
+        utils.change_deleted_column_type_to_id_type(engine, table_name,
+                                                    foo=fooColumn)
+
+        table = utils.get_table(engine, table_name)
+        # NOTE(boris-42): There is no way to check has foo type CustomType.
+        #                 but sqlalchemy will set it to NullType.
+        self.assertTrue(isinstance(table.c.foo.type, NullType))
+        self.assertTrue(isinstance(table.c.deleted.type, Integer))
+
+    def test_change_deleted_column_type_to_boolean(self):
+        table_name = 'abc'
+        for key, engine in self.engines.items():
+            meta = MetaData()
+            meta.bind = engine
+            table = Table(table_name, meta,
+                          Column('id', Integer, primary_key=True),
+                          Column('deleted', Integer))
+            table.create()
+
+            utils.change_deleted_column_type_to_boolean(engine, table_name)
+
+            table = utils.get_table(engine, table_name)
+            expected_type = Boolean if key != "mysql" else mysql.TINYINT
+            self.assertTrue(isinstance(table.c.deleted.type, expected_type))
+
+    def test_change_deleted_column_type_to_boolean_type_custom(self):
+        table_name = 'abc'
+        engine = self.engines['sqlite']
+        meta = MetaData()
+        meta.bind = engine
+        table = Table(table_name, meta,
+                      Column('id', Integer, primary_key=True),
+                      Column('foo', CustomType),
+                      Column('deleted', Integer))
+        table.create()
+
+        self.assertRaises(exception.NovaException,
+                          utils.change_deleted_column_type_to_boolean,
+                          engine, table_name)
+
+        fooColumn = Column('foo', CustomType())
+        utils.change_deleted_column_type_to_boolean(engine, table_name,
+                                                    foo=fooColumn)
+
+        table = utils.get_table(engine, table_name)
+        # NOTE(boris-42): There is no way to check has foo type CustomType.
+        #                 but sqlalchemy will set it to NullType.
+        self.assertTrue(isinstance(table.c.foo.type, NullType))
+        self.assertTrue(isinstance(table.c.deleted.type, Boolean))