OpenStack Study: migration_helpers.py

**** CubicPower OpenStack Study ****

def get_constraints_names(table, column_name):

    fkeys = [fk.name for fk in table.constraints

             if (column_name in fk.columns and

                 isinstance(fk, sqlalchemy.ForeignKeyConstraint))]

    return fkeys

#  remove_constraints and add_constraints both accept a list of dictionaries

#  that contain:

#  {'table': a sqlalchemy table. The constraint is added to to dropped from

#           this table.

#  'fk_column': the name of a column on the above table,  The constraint

#               is added to or dropped from this column

#  'ref_column':a sqlalchemy column object.  This is the reference column

#               for the constraint.

**** CubicPower OpenStack Study ****

def remove_constraints(constraints):

    for constraint_def in constraints:

        constraint_names = get_constraints_names(constraint_def['table'],

                                                 constraint_def['fk_column'])

        for constraint_name in constraint_names:

            migrate.ForeignKeyConstraint(

                columns=[getattr(constraint_def['table'].c,

                                 constraint_def['fk_column'])],

                refcolumns=[constraint_def['ref_column']],

                name=constraint_name).drop()

**** CubicPower OpenStack Study ****

def add_constraints(constraints):

    for constraint_def in constraints:

        if constraint_def['table'].kwargs.get('mysql_engine') == 'MyISAM':

            # Don't try to create constraint when using MyISAM because it's

            # not supported.

            continue

        ref_col = constraint_def['ref_column']

        ref_engine = ref_col.table.kwargs.get('mysql_engine')

        if ref_engine == 'MyISAM':

            # Don't try to create constraint when using MyISAM because it's

            # not supported.

            continue

        migrate.ForeignKeyConstraint(

            columns=[getattr(constraint_def['table'].c,

                             constraint_def['fk_column'])],

            refcolumns=[constraint_def['ref_column']]).create()

**** CubicPower OpenStack Study ****

def rename_tables_with_constraints(renames, constraints, engine):

    """Renames tables with foreign key constraints.

    Tables are renamed after first removing constraints. The constraints are

    replaced after the rename is complete.

    This works on databases that don't support renaming tables that have

    constraints on them (DB2).

    `renames` is a dict, mapping {'to_table_name': from_table, ...}

    """

    if engine.name != 'sqlite':

        # Sqlite doesn't support constraints, so nothing to remove.

        remove_constraints(constraints)

    for to_table_name in renames:

        from_table = renames[to_table_name]

        from_table.rename(to_table_name)

    if engine != 'sqlite':

        add_constraints(constraints)

**** CubicPower OpenStack Study ****

def find_migrate_repo(package=None, repo_name='migrate_repo'):

    package = package or sql

    path = os.path.abspath(os.path.join(

        os.path.dirname(package.__file__), repo_name))

    if os.path.isdir(path):

        return path

    raise exception.MigrationNotProvided(package.__name__, path)

**** CubicPower OpenStack Study ****

def sync_database_to_version(extension=None, version=None):

    if not extension:

        abs_path = find_migrate_repo()

    else:

        try:

            package_name = '.'.join((contrib.__name__, extension))

            package = importutils.import_module(package_name)

        except ImportError:

            raise ImportError(_("%s extension does not exist.")

                              % package_name)

        try:

            abs_path = find_migrate_repo(package)

            try:

                migration.db_version_control(sql.get_engine(), abs_path)

            # Register the repo with the version control API

            # If it already knows about the repo, it will throw

            # an exception that we can safely ignore

            except exceptions.DatabaseAlreadyControlledError:

                pass

        except exception.MigrationNotProvided as e:

            print(e)

            sys.exit(1)

    migration.db_sync(sql.get_engine(), abs_path, version=version)

**** CubicPower OpenStack Study ****

def get_db_version(extension=None):

    if not extension:

        return migration.db_version(sql.get_engine(), find_migrate_repo(), 0)

    try:

        package_name = '.'.join((contrib.__name__, extension))

        package = importutils.import_module(package_name)

    except ImportError:

        raise ImportError(_("%s extension does not exist.")

                          % package_name)

    return migration.db_version(

        sql.get_engine(), find_migrate_repo(package), 0)

**** CubicPower OpenStack Study ****

def print_db_version(extension=None):

    try:

        db_version = get_db_version(extension=extension)

        print(db_version)

    except exception.MigrationNotProvided as e:

        print(e)

        sys.exit(1)