Python sqlalchemy.types 模块，PickleType() 实例源码

def __init__(self, namespace, url=None, sa_opts=None, optimistic=False,
                 table_name='beaker_cache', data_dir=None, lock_dir=None,
                 **params):
        """Creates a database namespace manager

        ``url``
            SQLAlchemy compliant db url
        ``sa_opts``
            A dictionary of SQLAlchemy keyword options to initialize the engine
            with.
        ``optimistic``
            Use optimistic session locking, note that this will result in an
            additional select when updating a cache value to compare version
            numbers.
        ``table_name``
            The table name to use in the database for the cache.
        """
        OpenResourceNamespaceManager.__init__(self, namespace)

        if sa_opts is None:
            sa_opts = params

        if lock_dir:
            self.lock_dir = lock_dir
        elif data_dir:
            self.lock_dir = data_dir + "/container_db_lock"
        if self.lock_dir:
            verify_directory(self.lock_dir)            

        # Check to see if the table's been created before
        url = url or sa_opts['sa.url']
        table_key = url + table_name
        def make_cache():
            # Check to see if we have a connection pool open already
            meta_key = url + table_name
            def make_meta():
                # SQLAlchemy pops the url, this ensures it sticks around
                # later
                sa_opts['sa.url'] = url
                engine = sa.engine_from_config(sa_opts, 'sa.')
                meta = sa.MetaData()
                meta.bind = engine
                return meta
            meta = DatabaseNamespaceManager.metadatas.get(meta_key, make_meta)
            # Create the table object and cache it now
            cache = sa.Table(table_name, meta,
                             sa.Column('id', types.Integer, primary_key=True),
                             sa.Column('namespace', types.String(255), nullable=False),
                             sa.Column('accessed', types.DateTime, nullable=False),
                             sa.Column('created', types.DateTime, nullable=False),
                             sa.Column('data', types.PickleType, nullable=False),
                             sa.UniqueConstraint('namespace')
            )
            cache.create(checkfirst=True)
            return cache
        self.hash = {}
        self._is_new = False
        self.loaded = False
        self.cache = DatabaseNamespaceManager.tables.get(table_key, make_cache)