"""

        # prefix, repo_name, suffix

        return self._cache_key_partition()[2]

    @classmethod

    def clear_cache(cls):

        """

        Delete all cache keys from database.

        Should only be run when all instances are down and all entries thus stale.

        """

        cls.query().delete()

        Session().commit()

    @classmethod

    def _get_cache_key(cls, key):

        """

        Wrapper for generating a unique cache key for this instance and "key".

        key must / will start with a repo_name which will be stored in .cache_args .

        """

        import kallithea

        prefix = kallithea.CONFIG.get('instance_id', '')

        return "%s%s" % (prefix, key)

    @classmethod

    def set_invalidate(cls, repo_name, delete=False):

        """

        Mark all caches of a repo as invalid in the database.

        """

        inv_objs = Session().query(cls).filter(cls.cache_args == repo_name).all()

        log.debug('for repo %s got %s invalidation objects'

                  % (safe_str(repo_name), inv_objs))

        for inv_obj in inv_objs:

            log.debug('marking %s key for invalidation based on repo_name=%s'

                      % (inv_obj, safe_str(repo_name)))

            if delete:

                Session().delete(inv_obj)

            else:

                inv_obj.cache_active = False

                Session().add(inv_obj)

        Session().commit()

    @classmethod

    def test_and_set_valid(cls, repo_name, kind, valid_cache_keys=None):

        """

        Mark this cache key as active and currently cached.

        Return True if the existing cache registration still was valid.

        Return False to indicate that it had been invalidated and caches should be refreshed.

        """

        key = (repo_name + '_' + kind) if kind else repo_name

        cache_key = cls._get_cache_key(key)

        if valid_cache_keys and cache_key in valid_cache_keys:

            return True

        inv_obj = cls.query().filter(cls.cache_key == cache_key).scalar()

        if not inv_obj:

            inv_obj = CacheInvalidation(cache_key, repo_name)

        if inv_obj.cache_active:

            return True

        inv_obj.cache_active = True

        Session().add(inv_obj)

        Session().commit()

        return False

    @classmethod

    def get_valid_cache_keys(cls):

        """

        Return opaque object with information of which caches still are valid

        and can be used without checking for invalidation.

        """

        return set(inv_obj.cache_key for inv_obj in cls.query().filter(cls.cache_active).all())

class ChangesetComment(Base, BaseModel):

    __tablename__ = 'changeset_comments'

    __table_args__ = (

        Index('cc_revision_idx', 'revision'),

        {'extend_existing': True, 'mysql_engine': 'InnoDB',

         'mysql_charset': 'utf8', 'sqlite_autoincrement': True},

    )

    comment_id = Column('comment_id', Integer(), nullable=False, primary_key=True)

    repo_id = Column('repo_id', Integer(), ForeignKey('repositories.repo_id'), nullable=False)

    revision = Column('revision', String(40), nullable=True)

    pull_request_id = Column("pull_request_id", Integer(), ForeignKey('pull_requests.pull_request_id'), nullable=True)

    line_no = Column('line_no', Unicode(10), nullable=True)

    hl_lines = Column('hl_lines', Unicode(512), nullable=True)

    f_path = Column('f_path', Unicode(1000), nullable=True)

    user_id = Column('user_id', Integer(), ForeignKey('users.user_id'), nullable=False)

    text = Column('text', UnicodeText(25000), nullable=False)

    created_on = Column('created_on', DateTime(timezone=False), nullable=False, default=datetime.datetime.now)

    modified_at = Column('modified_at', DateTime(timezone=False), nullable=False, default=datetime.datetime.now)

    author = relationship('User', lazy='joined')

    repo = relationship('Repository')

    pull_request = relationship('PullRequest')

    @classmethod

    def get_users(cls, revision=None, pull_request_id=None):

        """

        Returns user associated with this ChangesetComment. ie those

        who actually commented

        :param cls:

        :param revision:

        """

        q = Session().query(User)\

                .join(ChangesetComment.author)

        if revision:

            q = q.filter(cls.revision == revision)

        elif pull_request_id:

            q = q.filter(cls.pull_request_id == pull_request_id)

        return q.all()

class ChangesetStatus(Base, BaseModel):

    __tablename__ = 'changeset_statuses'

    __table_args__ = (

        Index('cs_revision_idx', 'revision'),

        Index('cs_version_idx', 'version'),

        UniqueConstraint('repo_id', 'revision', 'version'),

        {'extend_existing': True, 'mysql_engine': 'InnoDB',

         'mysql_charset': 'utf8', 'sqlite_autoincrement': True}

    )

    STATUS_NOT_REVIEWED = DEFAULT = 'not_reviewed'

    STATUS_APPROVED = 'approved'

    STATUS_REJECTED = 'rejected'

    STATUS_UNDER_REVIEW = 'under_review'

    STATUSES = [

        (STATUS_NOT_REVIEWED, _("Not Reviewed")),  # (no icon) and default

        (STATUS_APPROVED, _("Approved")),

        (STATUS_REJECTED, _("Rejected")),

        (STATUS_UNDER_REVIEW, _("Under Review")),

    ]

    changeset_status_id = Column('changeset_status_id', Integer(), nullable=False, primary_key=True)

    repo_id = Column('repo_id', Integer(), ForeignKey('repositories.repo_id'), nullable=False)

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

    revision = Column('revision', String(40), nullable=False)

    status = Column('status', String(128), nullable=False, default=DEFAULT)

    changeset_comment_id = Column('changeset_comment_id', Integer(), ForeignKey('changeset_comments.comment_id'))

    modified_at = Column('modified_at', DateTime(), nullable=False, default=datetime.datetime.now)

    version = Column('version', Integer(), nullable=False, default=0)

    pull_request_id = Column("pull_request_id", Integer(), ForeignKey('pull_requests.pull_request_id'), nullable=True)

    author = relationship('User', lazy='joined')

    repo = relationship('Repository')

    comment = relationship('ChangesetComment', lazy='joined')

    pull_request = relationship('PullRequest')

    def __unicode__(self):

        return u"<%s('%s:%s')>" % (

            self.__class__.__name__,

            self.status, self.author

        )

    @classmethod

    def get_status_lbl(cls, value):

        return dict(cls.STATUSES).get(value)

    @property

    def status_lbl(self):

        return ChangesetStatus.get_status_lbl(self.status)

class PullRequest(Base, BaseModel):

    __tablename__ = 'pull_requests'

    __table_args__ = (

        {'extend_existing': True, 'mysql_engine': 'InnoDB',

         'mysql_charset': 'utf8', 'sqlite_autoincrement': True},

    )

    # values for .status

    STATUS_NEW = u'new'

    STATUS_CLOSED = u'closed'

    pull_request_id = Column('pull_request_id', Integer(), nullable=False, primary_key=True)

    title = Column('title', Unicode(256), nullable=True)

    description = Column('description', UnicodeText(10240), nullable=True)

    status = Column('status', Unicode(256), nullable=False, default=STATUS_NEW) # only for closedness, not approve/reject/etc

    created_on = Column('created_on', DateTime(timezone=False), nullable=False, default=datetime.datetime.now)

    updated_on = Column('updated_on', DateTime(timezone=False), nullable=False, default=datetime.datetime.now)

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

    _revisions = Column('revisions', UnicodeText(20500))  # 500 revisions max

    org_repo_id = Column('org_repo_id', Integer(), ForeignKey('repositories.repo_id'), nullable=False)

    org_ref = Column('org_ref', Unicode(256), nullable=False)

    other_repo_id = Column('other_repo_id', Integer(), ForeignKey('repositories.repo_id'), nullable=False)

    other_ref = Column('other_ref', Unicode(256), nullable=False)

    @hybrid_property