# ext/asyncio/session.py # Copyright (C) 2020-2023 the SQLAlchemy authors and contributors # # # This module is part of SQLAlchemy and is released under # the MIT License: https://www.opensource.org/licenses/mit-license.php import asyncio from . import engine from . import result as _result from .base import ReversibleProxy from .base import StartableContext from .result import _ensure_sync_result from ... import util from ...orm import object_session from ...orm import Session from ...orm import state as _instance_state from ...util.concurrency import greenlet_spawn _EXECUTE_OPTIONS = util.immutabledict({"prebuffer_rows": True}) _STREAM_OPTIONS = util.immutabledict({"stream_results": True}) @util.create_proxy_methods( Session, ":class:`_orm.Session`", ":class:`_asyncio.AsyncSession`", classmethods=["object_session", "identity_key"], methods=[ "__contains__", "__iter__", "add", "add_all", "expire", "expire_all", "expunge", "expunge_all", "is_modified", "in_transaction", "in_nested_transaction", ], attributes=[ "dirty", "deleted", "new", "identity_map", "is_active", "autoflush", "no_autoflush", "info", ], ) class AsyncSession(ReversibleProxy): """Asyncio version of :class:`_orm.Session`. The :class:`_asyncio.AsyncSession` is a proxy for a traditional :class:`_orm.Session` instance. .. versionadded:: 1.4 To use an :class:`_asyncio.AsyncSession` with custom :class:`_orm.Session` implementations, see the :paramref:`_asyncio.AsyncSession.sync_session_class` parameter. """ _is_asyncio = True dispatch = None def __init__(self, bind=None, binds=None, sync_session_class=None, **kw): r"""Construct a new :class:`_asyncio.AsyncSession`. All parameters other than ``sync_session_class`` are passed to the ``sync_session_class`` callable directly to instantiate a new :class:`_orm.Session`. Refer to :meth:`_orm.Session.__init__` for parameter documentation. :param sync_session_class: A :class:`_orm.Session` subclass or other callable which will be used to construct the :class:`_orm.Session` which will be proxied. This parameter may be used to provide custom :class:`_orm.Session` subclasses. Defaults to the :attr:`_asyncio.AsyncSession.sync_session_class` class-level attribute. .. versionadded:: 1.4.24 """ kw["future"] = True if bind: self.bind = bind bind = engine._get_sync_engine_or_connection(bind) if binds: self.binds = binds binds = { key: engine._get_sync_engine_or_connection(b) for key, b in binds.items() } if sync_session_class: self.sync_session_class = sync_session_class self.sync_session = self._proxied = self._assign_proxied( self.sync_session_class(bind=bind, binds=binds, **kw) ) sync_session_class = Session """The class or callable that provides the underlying :class:`_orm.Session` instance for a particular :class:`_asyncio.AsyncSession`. At the class level, this attribute is the default value for the :paramref:`_asyncio.AsyncSession.sync_session_class` parameter. Custom subclasses of :class:`_asyncio.AsyncSession` can override this. At the instance level, this attribute indicates the current class or callable that was used to provide the :class:`_orm.Session` instance for this :class:`_asyncio.AsyncSession` instance. .. versionadded:: 1.4.24 """ sync_session: Session """Reference to the underlying :class:`_orm.Session` this :class:`_asyncio.AsyncSession` proxies requests towards. This instance can be used as an event target. .. seealso:: :ref:`asyncio_events` """ async def refresh( self, instance, attribute_names=None, with_for_update=None ): """Expire and refresh the attributes on the given instance. A query will be issued to the database and all attributes will be refreshed with their current database value. This is the async version of the :meth:`_orm.Session.refresh` method. See that method for a complete description of all options. .. seealso:: :meth:`_orm.Session.refresh` - main documentation for refresh """ return await greenlet_spawn( self.sync_session.refresh, instance, attribute_names=attribute_names, with_for_update=with_for_update, ) async def run_sync(self, fn, *arg, **kw): """Invoke the given sync callable passing sync self as the first argument. This method maintains the asyncio event loop all the way through to the database connection by running the given callable in a specially instrumented greenlet. E.g.:: with AsyncSession(async_engine) as session: await session.run_sync(some_business_method) .. note:: The provided callable is invoked inline within the asyncio event loop, and will block on traditional IO calls. IO within this callable should only call into SQLAlchemy's asyncio database APIs which will be properly adapted to the greenlet context. .. seealso:: :ref:`session_run_sync` """ return await greenlet_spawn(fn, self.sync_session, *arg, **kw) async def execute( self, statement, params=None, execution_options=util.EMPTY_DICT, bind_arguments=None, **kw ): """Execute a statement and return a buffered :class:`_engine.Result` object. .. seealso:: :meth:`_orm.Session.execute` - main documentation for execute """ if execution_options: execution_options = util.immutabledict(execution_options).union( _EXECUTE_OPTIONS ) else: execution_options = _EXECUTE_OPTIONS result = await greenlet_spawn( self.sync_session.execute, statement, params=params, execution_options=execution_options, bind_arguments=bind_arguments, **kw ) return await _ensure_sync_result(result, self.execute) async def scalar( self, statement, params=None, execution_options=util.EMPTY_DICT, bind_arguments=None, **kw ): """Execute a statement and return a scalar result. .. seealso:: :meth:`_orm.Session.scalar` - main documentation for scalar """ result = await self.execute( statement, params=params, execution_options=execution_options, bind_arguments=bind_arguments, **kw ) return result.scalar() async def scalars( self, statement, params=None, execution_options=util.EMPTY_DICT, bind_arguments=None, **kw ): """Execute a statement and return scalar results. :return: a :class:`_result.ScalarResult` object .. versionadded:: 1.4.24 Added :meth:`_asyncio.AsyncSession.scalars` .. versionadded:: 1.4.26 Added :meth:`_asyncio.async_scoped_session.scalars` .. seealso:: :meth:`_orm.Session.scalars` - main documentation for scalars :meth:`_asyncio.AsyncSession.stream_scalars` - streaming version """ result = await self.execute( statement, params=params, execution_options=execution_options, bind_arguments=bind_arguments, **kw ) return result.scalars() async def get( self, entity, ident, options=None, populate_existing=False, with_for_update=None, identity_token=None, ): """Return an instance based on the given primary key identifier, or ``None`` if not found. .. seealso:: :meth:`_orm.Session.get` - main documentation for get """ return await greenlet_spawn( self.sync_session.get, entity, ident, options=options, populate_existing=populate_existing, with_for_update=with_for_update, identity_token=identity_token, ) async def stream( self, statement, params=None, execution_options=util.EMPTY_DICT, bind_arguments=None, **kw ): """Execute a statement and return a streaming :class:`_asyncio.AsyncResult` object. """ if execution_options: execution_options = util.immutabledict(execution_options).union( _STREAM_OPTIONS ) else: execution_options = _STREAM_OPTIONS result = await greenlet_spawn( self.sync_session.execute, statement, params=params, execution_options=execution_options, bind_arguments=bind_arguments, **kw ) return _result.AsyncResult(result) async def stream_scalars( self, statement, params=None, execution_options=util.EMPTY_DICT, bind_arguments=None, **kw ): """Execute a statement and return a stream of scalar results. :return: an :class:`_asyncio.AsyncScalarResult` object .. versionadded:: 1.4.24 .. seealso:: :meth:`_orm.Session.scalars` - main documentation for scalars :meth:`_asyncio.AsyncSession.scalars` - non streaming version """ result = await self.stream( statement, params=params, execution_options=execution_options, bind_arguments=bind_arguments, **kw ) return result.scalars() async def delete(self, instance): """Mark an instance as deleted. The database delete operation occurs upon ``flush()``. As this operation may need to cascade along unloaded relationships, it is awaitable to allow for those queries to take place. .. seealso:: :meth:`_orm.Session.delete` - main documentation for delete """ return await greenlet_spawn(self.sync_session.delete, instance) async def merge(self, instance, load=True, options=None): """Copy the state of a given instance into a corresponding instance within this :class:`_asyncio.AsyncSession`. .. seealso:: :meth:`_orm.Session.merge` - main documentation for merge """ return await greenlet_spawn( self.sync_session.merge, instance, load=load, options=options ) async def flush(self, objects=None): """Flush all the object changes to the database. .. seealso:: :meth:`_orm.Session.flush` - main documentation for flush """ await greenlet_spawn(self.sync_session.flush, objects=objects) def get_transaction(self): """Return the current root transaction in progress, if any. :return: an :class:`_asyncio.AsyncSessionTransaction` object, or ``None``. .. versionadded:: 1.4.18 """ trans = self.sync_session.get_transaction() if trans is not None: return AsyncSessionTransaction._retrieve_proxy_for_target(trans) else: return None def get_nested_transaction(self): """Return the current nested transaction in progress, if any. :return: an :class:`_asyncio.AsyncSessionTransaction` object, or ``None``. .. versionadded:: 1.4.18 """ trans = self.sync_session.get_nested_transaction() if trans is not None: return AsyncSessionTransaction._retrieve_proxy_for_target(trans) else: return None def get_bind(self, mapper=None, clause=None, bind=None, **kw): """Return a "bind" to which the synchronous proxied :class:`_orm.Session` is bound. Unlike the :meth:`_orm.Session.get_bind` method, this method is currently **not** used by this :class:`.AsyncSession` in any way in order to resolve engines for requests. .. note:: This method proxies directly to the :meth:`_orm.Session.get_bind` method, however is currently **not** useful as an override target, in contrast to that of the :meth:`_orm.Session.get_bind` method. The example below illustrates how to implement custom :meth:`_orm.Session.get_bind` schemes that work with :class:`.AsyncSession` and :class:`.AsyncEngine`. The pattern introduced at :ref:`session_custom_partitioning` illustrates how to apply a custom bind-lookup scheme to a :class:`_orm.Session` given a set of :class:`_engine.Engine` objects. To apply a corresponding :meth:`_orm.Session.get_bind` implementation for use with a :class:`.AsyncSession` and :class:`.AsyncEngine` objects, continue to subclass :class:`_orm.Session` and apply it to :class:`.AsyncSession` using :paramref:`.AsyncSession.sync_session_class`. The inner method must continue to return :class:`_engine.Engine` instances, which can be acquired from a :class:`_asyncio.AsyncEngine` using the :attr:`_asyncio.AsyncEngine.sync_engine` attribute:: # using example from "Custom Vertical Partitioning" import random from sqlalchemy.ext.asyncio import AsyncSession from sqlalchemy.ext.asyncio import create_async_engine from sqlalchemy.orm import Session, sessionmaker # construct async engines w/ async drivers engines = { 'leader':create_async_engine("sqlite+aiosqlite:///leader.db"), 'other':create_async_engine("sqlite+aiosqlite:///other.db"), 'follower1':create_async_engine("sqlite+aiosqlite:///follower1.db"), 'follower2':create_async_engine("sqlite+aiosqlite:///follower2.db"), } class RoutingSession(Session): def get_bind(self, mapper=None, clause=None, **kw): # within get_bind(), return sync engines if mapper and issubclass(mapper.class_, MyOtherClass): return engines['other'].sync_engine elif self._flushing or isinstance(clause, (Update, Delete)): return engines['leader'].sync_engine else: return engines[ random.choice(['follower1','follower2']) ].sync_engine # apply to AsyncSession using sync_session_class AsyncSessionMaker = sessionmaker( class_=AsyncSession, sync_session_class=RoutingSession ) The :meth:`_orm.Session.get_bind` method is called in a non-asyncio, implicitly non-blocking context in the same manner as ORM event hooks and functions that are invoked via :meth:`.AsyncSession.run_sync`, so routines that wish to run SQL commands inside of :meth:`_orm.Session.get_bind` can continue to do so using blocking-style code, which will be translated to implicitly async calls at the point of invoking IO on the database drivers. """ # noqa: E501 return self.sync_session.get_bind( mapper=mapper, clause=clause, bind=bind, **kw ) async def connection(self, **kw): r"""Return a :class:`_asyncio.AsyncConnection` object corresponding to this :class:`.Session` object's transactional state. This method may also be used to establish execution options for the database connection used by the current transaction. .. versionadded:: 1.4.24 Added \**kw arguments which are passed through to the underlying :meth:`_orm.Session.connection` method. .. seealso:: :meth:`_orm.Session.connection` - main documentation for "connection" """ sync_connection = await greenlet_spawn( self.sync_session.connection, **kw ) return engine.AsyncConnection._retrieve_proxy_for_target( sync_connection ) def begin(self, **kw): """Return an :class:`_asyncio.AsyncSessionTransaction` object. The underlying :class:`_orm.Session` will perform the "begin" action when the :class:`_asyncio.AsyncSessionTransaction` object is entered:: async with async_session.begin(): # .. ORM transaction is begun Note that database IO will not normally occur when the session-level transaction is begun, as database transactions begin on an on-demand basis. However, the begin block is async to accommodate for a :meth:`_orm.SessionEvents.after_transaction_create` event hook that may perform IO. For a general description of ORM begin, see :meth:`_orm.Session.begin`. """ return AsyncSessionTransaction(self) def begin_nested(self, **kw): """Return an :class:`_asyncio.AsyncSessionTransaction` object which will begin a "nested" transaction, e.g. SAVEPOINT. Behavior is the same as that of :meth:`_asyncio.AsyncSession.begin`. For a general description of ORM begin nested, see :meth:`_orm.Session.begin_nested`. """ return AsyncSessionTransaction(self, nested=True) async def rollback(self): """Rollback the current transaction in progress.""" return await greenlet_spawn(self.sync_session.rollback) async def commit(self): """Commit the current transaction in progress.""" return await greenlet_spawn(self.sync_session.commit) async def close(self): """Close out the transactional resources and ORM objects used by this :class:`_asyncio.AsyncSession`. This expunges all ORM objects associated with this :class:`_asyncio.AsyncSession`, ends any transaction in progress and :term:`releases` any :class:`_asyncio.AsyncConnection` objects which this :class:`_asyncio.AsyncSession` itself has checked out from associated :class:`_asyncio.AsyncEngine` objects. The operation then leaves the :class:`_asyncio.AsyncSession` in a state which it may be used again. .. tip:: The :meth:`_asyncio.AsyncSession.close` method **does not prevent the Session from being used again**. The :class:`_asyncio.AsyncSession` itself does not actually have a distinct "closed" state; it merely means the :class:`_asyncio.AsyncSession` will release all database connections and ORM objects. .. seealso:: :ref:`session_closing` - detail on the semantics of :meth:`_asyncio.AsyncSession.close` """ await greenlet_spawn(self.sync_session.close) async def invalidate(self): """Close this Session, using connection invalidation. For a complete description, see :meth:`_orm.Session.invalidate`. """ return await greenlet_spawn(self.sync_session.invalidate) @classmethod async def close_all(self): """Close all :class:`_asyncio.AsyncSession` sessions.""" return await greenlet_spawn(self.sync_session.close_all) async def __aenter__(self): return self async def __aexit__(self, type_, value, traceback): task = asyncio.get_event_loop().create_task(self.close()) await asyncio.shield(task) def _maker_context_manager(self): # no @contextlib.asynccontextmanager until python3.7, gr return _AsyncSessionContextManager(self) class _AsyncSessionContextManager: def __init__(self, async_session): self.async_session = async_session async def __aenter__(self): self.trans = self.async_session.begin() await self.trans.__aenter__() return self.async_session async def __aexit__(self, type_, value, traceback): async def go(): await self.trans.__aexit__(type_, value, traceback) await self.async_session.__aexit__(type_, value, traceback) task = asyncio.get_event_loop().create_task(go()) await asyncio.shield(task) class AsyncSessionTransaction(ReversibleProxy, StartableContext): """A wrapper for the ORM :class:`_orm.SessionTransaction` object. This object is provided so that a transaction-holding object for the :meth:`_asyncio.AsyncSession.begin` may be returned. The object supports both explicit calls to :meth:`_asyncio.AsyncSessionTransaction.commit` and :meth:`_asyncio.AsyncSessionTransaction.rollback`, as well as use as an async context manager. .. versionadded:: 1.4 """ __slots__ = ("session", "sync_transaction", "nested") def __init__(self, session, nested=False): self.session = session self.nested = nested self.sync_transaction = None @property def is_active(self): return ( self._sync_transaction() is not None and self._sync_transaction().is_active ) def _sync_transaction(self): if not self.sync_transaction: self._raise_for_not_started() return self.sync_transaction async def rollback(self): """Roll back this :class:`_asyncio.AsyncTransaction`.""" await greenlet_spawn(self._sync_transaction().rollback) async def commit(self): """Commit this :class:`_asyncio.AsyncTransaction`.""" await greenlet_spawn(self._sync_transaction().commit) async def start(self, is_ctxmanager=False): self.sync_transaction = self._assign_proxied( await greenlet_spawn( self.session.sync_session.begin_nested if self.nested else self.session.sync_session.begin ) ) if is_ctxmanager: self.sync_transaction.__enter__() return self async def __aexit__(self, type_, value, traceback): await greenlet_spawn( self._sync_transaction().__exit__, type_, value, traceback ) def async_object_session(instance): """Return the :class:`_asyncio.AsyncSession` to which the given instance belongs. This function makes use of the sync-API function :class:`_orm.object_session` to retrieve the :class:`_orm.Session` which refers to the given instance, and from there links it to the original :class:`_asyncio.AsyncSession`. If the :class:`_asyncio.AsyncSession` has been garbage collected, the return value is ``None``. This functionality is also available from the :attr:`_orm.InstanceState.async_session` accessor. :param instance: an ORM mapped instance :return: an :class:`_asyncio.AsyncSession` object, or ``None``. .. versionadded:: 1.4.18 """ session = object_session(instance) if session is not None: return async_session(session) else: return None def async_session(session): """Return the :class:`_asyncio.AsyncSession` which is proxying the given :class:`_orm.Session` object, if any. :param session: a :class:`_orm.Session` instance. :return: a :class:`_asyncio.AsyncSession` instance, or ``None``. .. versionadded:: 1.4.18 """ return AsyncSession._retrieve_proxy_for_target(session, regenerate=False) _instance_state._async_provider = async_session