185 lines
6.3 KiB
Python
185 lines
6.3 KiB
Python
# orm/scoping.py
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# Copyright (C) 2005-2017 the SQLAlchemy authors and contributors
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# <see AUTHORS file>
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#
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# This module is part of SQLAlchemy and is released under
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# the MIT License: http://www.opensource.org/licenses/mit-license.php
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from .. import exc as sa_exc
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from ..util import ScopedRegistry, ThreadLocalRegistry, warn
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from . import class_mapper, exc as orm_exc
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from .session import Session
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__all__ = ['scoped_session']
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class scoped_session(object):
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"""Provides scoped management of :class:`.Session` objects.
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See :ref:`unitofwork_contextual` for a tutorial.
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"""
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session_factory = None
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"""The `session_factory` provided to `__init__` is stored in this
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attribute and may be accessed at a later time. This can be useful when
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a new non-scoped :class:`.Session` or :class:`.Connection` to the
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database is needed."""
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def __init__(self, session_factory, scopefunc=None):
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"""Construct a new :class:`.scoped_session`.
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:param session_factory: a factory to create new :class:`.Session`
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instances. This is usually, but not necessarily, an instance
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of :class:`.sessionmaker`.
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:param scopefunc: optional function which defines
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the current scope. If not passed, the :class:`.scoped_session`
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object assumes "thread-local" scope, and will use
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a Python ``threading.local()`` in order to maintain the current
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:class:`.Session`. If passed, the function should return
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a hashable token; this token will be used as the key in a
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dictionary in order to store and retrieve the current
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:class:`.Session`.
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"""
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self.session_factory = session_factory
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if scopefunc:
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self.registry = ScopedRegistry(session_factory, scopefunc)
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else:
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self.registry = ThreadLocalRegistry(session_factory)
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def __call__(self, **kw):
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r"""Return the current :class:`.Session`, creating it
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using the :attr:`.scoped_session.session_factory` if not present.
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:param \**kw: Keyword arguments will be passed to the
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:attr:`.scoped_session.session_factory` callable, if an existing
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:class:`.Session` is not present. If the :class:`.Session` is present
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and keyword arguments have been passed,
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:exc:`~sqlalchemy.exc.InvalidRequestError` is raised.
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"""
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if kw:
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scope = kw.pop('scope', False)
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if scope is not None:
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if self.registry.has():
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raise sa_exc.InvalidRequestError(
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"Scoped session is already present; "
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"no new arguments may be specified.")
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else:
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sess = self.session_factory(**kw)
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self.registry.set(sess)
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return sess
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else:
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return self.session_factory(**kw)
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else:
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return self.registry()
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def remove(self):
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"""Dispose of the current :class:`.Session`, if present.
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This will first call :meth:`.Session.close` method
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on the current :class:`.Session`, which releases any existing
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transactional/connection resources still being held; transactions
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specifically are rolled back. The :class:`.Session` is then
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discarded. Upon next usage within the same scope,
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the :class:`.scoped_session` will produce a new
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:class:`.Session` object.
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"""
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if self.registry.has():
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self.registry().close()
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self.registry.clear()
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def configure(self, **kwargs):
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"""reconfigure the :class:`.sessionmaker` used by this
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:class:`.scoped_session`.
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See :meth:`.sessionmaker.configure`.
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"""
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if self.registry.has():
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warn('At least one scoped session is already present. '
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' configure() can not affect sessions that have '
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'already been created.')
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self.session_factory.configure(**kwargs)
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def query_property(self, query_cls=None):
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"""return a class property which produces a :class:`.Query` object
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against the class and the current :class:`.Session` when called.
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e.g.::
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Session = scoped_session(sessionmaker())
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class MyClass(object):
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query = Session.query_property()
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# after mappers are defined
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result = MyClass.query.filter(MyClass.name=='foo').all()
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Produces instances of the session's configured query class by
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default. To override and use a custom implementation, provide
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a ``query_cls`` callable. The callable will be invoked with
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the class's mapper as a positional argument and a session
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keyword argument.
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There is no limit to the number of query properties placed on
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a class.
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"""
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class query(object):
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def __get__(s, instance, owner):
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try:
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mapper = class_mapper(owner)
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if mapper:
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if query_cls:
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# custom query class
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return query_cls(mapper, session=self.registry())
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else:
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# session's configured query class
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return self.registry().query(mapper)
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except orm_exc.UnmappedClassError:
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return None
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return query()
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ScopedSession = scoped_session
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"""Old name for backwards compatibility."""
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def instrument(name):
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def do(self, *args, **kwargs):
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return getattr(self.registry(), name)(*args, **kwargs)
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return do
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for meth in Session.public_methods:
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setattr(scoped_session, meth, instrument(meth))
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def makeprop(name):
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def set(self, attr):
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setattr(self.registry(), name, attr)
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def get(self):
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return getattr(self.registry(), name)
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return property(get, set)
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for prop in ('bind', 'dirty', 'deleted', 'new', 'identity_map',
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'is_active', 'autoflush', 'no_autoflush', 'info'):
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setattr(scoped_session, prop, makeprop(prop))
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def clslevel(name):
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def do(cls, *args, **kwargs):
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return getattr(Session, name)(*args, **kwargs)
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return classmethod(do)
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for prop in ('close_all', 'object_session', 'identity_key'):
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setattr(scoped_session, prop, clslevel(prop))
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