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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: https://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 create_proxy_methods
from ..util import ScopedRegistry
from ..util import ThreadLocalRegistry
from ..util import warn
from ..util import warn_deprecated
__all__ = ["scoped_session", "ScopedSessionMixin"]
class ScopedSessionMixin:
@property
def _proxied(self):
return self.registry()
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)
else:
sess = self.registry()
if not self._support_async and sess._is_asyncio:
warn_deprecated(
"Using `scoped_session` with asyncio is deprecated and "
"will raise an error in a future version. "
"Please use `async_scoped_session` instead.",
"1.4.23",
)
return sess
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)
@create_proxy_methods(
Session,
":class:`_orm.Session`",
":class:`_orm.scoping.scoped_session`",
classmethods=["close_all", "object_session", "identity_key"],
methods=[
"__contains__",
"__iter__",
"add",
"add_all",
"begin",
"begin_nested",
"close",
"commit",
"connection",
"delete",
"execute",
"expire",
"expire_all",
"expunge",
"expunge_all",
"flush",
"get",
"get_bind",
"is_modified",
"bulk_save_objects",
"bulk_insert_mappings",
"bulk_update_mappings",
"merge",
"query",
"refresh",
"rollback",
"scalar",
"scalars",
],
attributes=[
"bind",
"dirty",
"deleted",
"new",
"identity_map",
"is_active",
"autoflush",
"no_autoflush",
"info",
"autocommit",
],
)
class scoped_session(ScopedSessionMixin):
"""Provides scoped management of :class:`.Session` objects.
See :ref:`unitofwork_contextual` for a tutorial.
.. note::
When using :ref:`asyncio_toplevel`, the async-compatible
:class:`_asyncio.async_scoped_session` class should be
used in place of :class:`.scoped_session`.
"""
_support_async = False
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 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 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:
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:
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."""
|
