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scoping.py
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# orm/scoping.py # Copyright (C) 2005-2021 the SQLAlchemy authors and contributors # <see AUTHORS file> # # This module is part of SQLAlchemy and is released under # the MIT License: http://www.opensource.org/licenses/mit-license.php from . import class_mapper from . import exc as orm_exc from .session import Session from .. import exc as sa_exc from ..util import ScopedRegistry from ..util import ThreadLocalRegistry from ..util import warn __all__ = ["scoped_session"] class scoped_session(object): """Provides scoped management of :class:`.Session` objects. See :ref:`unitofwork_contextual` for a tutorial. """ session_factory = None """The `session_factory` provided to `__init__` is stored in this attribute and may be accessed at a later time. This can be useful when a new non-scoped :class:`.Session` or :class:`_engine.Connection` to the database is needed.""" def __init__(self, session_factory, scopefunc=None): """Construct a new :class:`.scoped_session`. :param session_factory: a factory to create new :class:`.Session` instances. This is usually, but not necessarily, an instance of :class:`.sessionmaker`. :param scopefunc: optional function which defines the current scope. If not passed, the :class:`.scoped_session` object assumes "thread-local" scope, and will use a Python ``threading.local()`` in order to maintain the current :class:`.Session`. If passed, the function should return a hashable token; this token will be used as the key in a dictionary in order to store and retrieve the current :class:`.Session`. """ self.session_factory = session_factory if scopefunc: self.registry = ScopedRegistry(session_factory, scopefunc) else: self.registry = ThreadLocalRegistry(session_factory) def __call__(self, **kw): r"""Return the current :class:`.Session`, creating it using the :attr:`.scoped_session.session_factory` if not present. :param \**kw: Keyword arguments will be passed to the :attr:`.scoped_session.session_factory` callable, if an existing :class:`.Session` is not present. If the :class:`.Session` is present and keyword arguments have been passed, :exc:`~sqlalchemy.exc.InvalidRequestError` is raised. """ if kw: if self.registry.has(): raise sa_exc.InvalidRequestError( "Scoped session is already present; " "no new arguments may be specified." ) else: sess = self.session_factory(**kw) self.registry.set(sess) return sess else: return self.registry() def remove(self): """Dispose of the current :class:`.Session`, if present. This will first call :meth:`.Session.close` method on the current :class:`.Session`, which releases any existing transactional/connection resources still being held; transactions specifically are rolled back. The :class:`.Session` is then discarded. Upon next usage within the same scope, the :class:`.scoped_session` will produce a new :class:`.Session` object. """ if self.registry.has(): self.registry().close() self.registry.clear() def configure(self, **kwargs): """reconfigure the :class:`.sessionmaker` used by this :class:`.scoped_session`. See :meth:`.sessionmaker.configure`. """ if self.registry.has(): warn( "At least one scoped session is already present. " " configure() can not affect sessions that have " "already been created." ) self.session_factory.configure(**kwargs) def query_property(self, query_cls=None): """return a class property which produces a :class:`_query.Query` object against the class and the current :class:`.Session` when called. e.g.:: Session = scoped_session(sessionmaker()) class MyClass(object): query = Session.query_property() # after mappers are defined result = MyClass.query.filter(MyClass.name=='foo').all() Produces instances of the session's configured query class by default. To override and use a custom implementation, provide a ``query_cls`` callable. The callable will be invoked with the class's mapper as a positional argument and a session keyword argument. There is no limit to the number of query properties placed on a class. """ class query(object): def __get__(s, instance, owner): try: mapper = class_mapper(owner) if mapper: if query_cls: # custom query class return query_cls(mapper, session=self.registry()) else: # session's configured query class return self.registry().query(mapper) except orm_exc.UnmappedClassError: return None return query() ScopedSession = scoped_session """Old name for backwards compatibility.""" def instrument(name): def do(self, *args, **kwargs): return getattr(self.registry(), name)(*args, **kwargs) return do for meth in Session.public_methods: setattr(scoped_session, meth, instrument(meth)) def makeprop(name): def set_(self, attr): setattr(self.registry(), name, attr) def get(self): return getattr(self.registry(), name) return property(get, set_) for prop in ( "bind", "dirty", "deleted", "new", "identity_map", "is_active", "autoflush", "no_autoflush", "info", "autocommit", ): setattr(scoped_session, prop, makeprop(prop)) def clslevel(name): def do(cls, *args, **kwargs): return getattr(Session, name)(*args, **kwargs) return classmethod(do) for prop in ("close_all", "object_session", "identity_key"): setattr(scoped_session, prop, clslevel(prop))