all needed steps, to perform the upgrade

            """Those steps follow schema versions so for example schema 

            for example schema with seq 002 == step_2 and so on.

            """

import logging

import datetime

from sqlalchemy import *

from sqlalchemy.exc import DatabaseError

from sqlalchemy.orm import relation, backref, class_mapper

from sqlalchemy.orm.session import Session

from rhodecode.model.meta import Base

from rhodecode.model.db import BaseModel

from rhodecode.lib.dbmigrate.migrate import *

log = logging.getLogger(__name__)

def upgrade(migrate_engine):

    """ Upgrade operations go here. 

    Don't create your own engine; bind migrate_engine to your metadata

    """

    #==========================================================================

    # Add table `groups``

    #==========================================================================

    tblname = 'groups'

    class Group(Base, BaseModel):

        __tablename__ = 'groups'

        __table_args__ = (UniqueConstraint('group_name'), {'useexisting':True},)

        group_id = Column("group_id", Integer(), nullable=False, unique=True, default=None, primary_key=True)

        group_name = Column("group_name", String(length=None, convert_unicode=False, assert_unicode=None), nullable=False, unique=True, default=None)

        group_parent_id = Column("group_parent_id", Integer(), ForeignKey('groups.group_id'), nullable=True, unique=None, default=None)

        parent_group = relation('Group', remote_side=group_id)

        def __init__(self, group_name='', parent_group=None):

            self.group_name = group_name

            self.parent_group = parent_group

        def __repr__(self):

            return "<%s('%s:%s')>" % (self.__class__.__name__, self.group_id,

                                      self.group_name)

    Base.metadata.tables[tblname].create(migrate_engine)

    #==========================================================================

    # Add table `group_to_perm`

    #==========================================================================

    tblname = 'group_to_perm'

    class GroupToPerm(Base, BaseModel):

        __tablename__ = 'group_to_perm'

        __table_args__ = (UniqueConstraint('group_id', 'permission_id'), {'useexisting':True})

        group_to_perm_id = Column("group_to_perm_id", Integer(), nullable=False, unique=True, default=None, primary_key=True)

        user_id = Column("user_id", Integer(), ForeignKey('users.user_id'), nullable=False, unique=None, default=None)

        permission_id = Column("permission_id", Integer(), ForeignKey('permissions.permission_id'), nullable=False, unique=None, default=None)

        group_id = Column("group_id", Integer(), ForeignKey('groups.group_id'), nullable=False, unique=None, default=None)

        user = relation('User')

        permission = relation('Permission')

        group = relation('Group')

    Base.metadata.tables[tblname].create(migrate_engine)

    #==========================================================================

    # Upgrade of `repositories` table

    #==========================================================================    

    tblname = 'repositories'

    tbl = Table(tblname, MetaData(bind=migrate_engine), autoload=True,

                    autoload_with=migrate_engine)

    #ADD group_id column#

    group_id = Column("group_id", Integer(), ForeignKey(u'groups.group_id'),

                  nullable=True, unique=False, default=None)

    group_id.create(tbl, populate_default=True)

    return

def downgrade(migrate_engine):

    meta = MetaData()

    meta.bind = migrate_engine