OpenStack Study: 021_add_trust_to_token.py

**** CubicPower OpenStack Study ****

def downgrade_token_table_with_column_drop(meta, migrate_engine):

    token_table = sqlalchemy.Table('token', meta, autoload=True)

    #delete old tokens, as the format has changed.

    #We don't guarantee that existing tokens will be

    #usable after a migration

    token_table.delete()

    token_table.drop_column(

        sqlalchemy.Column('trust_id',

                          sqlalchemy.String(64),

                          nullable=True))

    token_table.drop_column(

        sqlalchemy.Column('user_id',

                          sqlalchemy.String(64)))

**** CubicPower OpenStack Study ****

def create_column_forgiving(migrate_engine, table, column):

    try:

        table.create_column(column)

    except exc.OperationalError as e:

        if (e.args[0].endswith('duplicate column name: %s' % column.name)

                and migrate_engine.name == "sqlite"):

                    #sqlite does not drop columns, so  if we have already

                    #done a downgrade and are now upgrading,  we will hit

                    #this: the SQLite driver previously reported success

                    #dropping the columns but it hasn't.

                    pass

        else:

            raise

**** CubicPower OpenStack Study ****

def upgrade_token_table(meta, migrate_engine):

    #delete old tokens, as the format has changed.

    #The existing tokens will not

    #support some of the list functions

    token_table = sqlalchemy.Table('token', meta, autoload=True)

    token_table.delete()

    create_column_forgiving(

        migrate_engine, token_table,

        sqlalchemy.Column('trust_id',

                          sqlalchemy.String(64),

                          nullable=True))

    create_column_forgiving(

        migrate_engine, token_table,

        sqlalchemy.Column('user_id', sqlalchemy.String(64)))

**** CubicPower OpenStack Study ****

def upgrade(migrate_engine):

    meta = sqlalchemy.MetaData()

    meta.bind = migrate_engine

    upgrade_token_table(meta, migrate_engine)

**** CubicPower OpenStack Study ****

def downgrade(migrate_engine):

    meta = sqlalchemy.MetaData()

    meta.bind = migrate_engine

    downgrade_token_table_with_column_drop(meta, migrate_engine)