@property

    def scm_instance(self):

        import kallithea

        full_cache = str2bool(kallithea.CONFIG.get('vcs_full_cache'))

        if full_cache:

            return self.scm_instance_cached()

        return self.__get_instance()

    def scm_instance_cached(self, valid_cache_keys=None):

        @cache_region('long_term')

        def _c(repo_name):

            return self.__get_instance()

        rn = self.repo_name

        valid = CacheInvalidation.test_and_set_valid(rn, None, valid_cache_keys=valid_cache_keys)

        if not valid:

            log.debug('Cache for %s invalidated, getting new object', rn)

            region_invalidate(_c, None, rn)

        else:

            log.debug('Getting scm_instance of %s from cache', rn)

        return _c(rn)

    def __get_instance(self):

        log.debug('Creating instance of %s repository from %s',

        backend = get_backend(alias)

        if alias == 'hg':

                           baseui=self._ui)

        else:

            repo = backend(repo_full_path, create=False)

        return repo

    def __json__(self):

        return dict(landing_rev = self.landing_rev)

class RepoGroup(Base, BaseModel):

    __tablename__ = 'groups'

    __table_args__ = (

        UniqueConstraint('group_name', 'group_parent_id'),

        CheckConstraint('group_id != group_parent_id'),

        _table_args_default_dict,

    )

    __mapper_args__ = {'order_by': 'group_name'}

    SEP = ' » '

    group_id = Column(Integer(), unique=True, primary_key=True)

    group_name = Column(Unicode(255), nullable=False, unique=True)

    group_parent_id = Column(Integer(), ForeignKey('groups.group_id'), nullable=True)

    group_description = Column(Unicode(10000), nullable=False)