Asynchronous I/O (asyncio)¶
Support for Python asyncio. Support for Core and ORM usage is included, using asyncio-compatible dialects.
New in version 1.4.
Warning
Please read Asyncio Platform Installation Notes (Including Apple M1) for important platform installation notes for many platforms, including Apple M1 Architecture.
See also
Asynchronous IO Support for Core and ORM - initial feature announcement
Asyncio Integration - example scripts illustrating working examples of Core and ORM use within the asyncio extension.
Asyncio Platform Installation Notes (Including Apple M1)¶
The asyncio extension requires Python 3 only. It also depends upon the greenlet library. This dependency is installed by default on common machine platforms including:
x86_64 aarch64 ppc64le amd64 win32For the above platforms, greenlet is known to supply pre-built wheel files.
For other platforms, greenlet does not install by default;
the current file listing for greenlet can be seen at
Greenlet - Download Files.
Note that there are many architectures omitted, including Apple M1.
To install SQLAlchemy while ensuring the greenlet dependency is present
regardless of what platform is in use, the
[asyncio] setuptools extra
may be installed
as follows, which will include also instruct pip to install greenlet:
pip install sqlalchemy[asyncio]Note that installation of greenlet on platforms that do not have a pre-built
wheel file means that greenlet will be built from source, which requires
that Python’s development libraries also be present.
Synopsis - Core¶
For Core use, the create_async_engine() function creates an
instance of AsyncEngine which then offers an async version of
the traditional Engine API. The
AsyncEngine delivers an AsyncConnection via
its AsyncEngine.connect() and AsyncEngine.begin()
methods which both deliver asynchronous context managers. The
AsyncConnection can then invoke statements using either the
AsyncConnection.execute() method to deliver a buffered
Result, or the AsyncConnection.stream() method
to deliver a streaming server-side AsyncResult:
>>> import asyncio
>>> from sqlalchemy import Column
>>> from sqlalchemy import MetaData
>>> from sqlalchemy import select
>>> from sqlalchemy import String
>>> from sqlalchemy import Table
>>> from sqlalchemy.ext.asyncio import create_async_engine
>>> meta = MetaData()
>>> t1 = Table("t1", meta, Column("name", String(50), primary_key=True))
>>> async def async_main() -> None:
... engine = create_async_engine("sqlite+aiosqlite://", echo=True)
...
... async with engine.begin() as conn:
... await conn.run_sync(meta.drop_all)
... await conn.run_sync(meta.create_all)
...
... await conn.execute(
... t1.insert(), [{"name": "some name 1"}, {"name": "some name 2"}]
... )
...
... async with engine.connect() as conn:
... # select a Result, which will be delivered with buffered
... # results
... result = await conn.execute(select(t1).where(t1.c.name == "some name 1"))
...
... print(result.fetchall())
...
... # for AsyncEngine created in function scope, close and
... # clean-up pooled connections
... await engine.dispose()
>>> asyncio.run(async_main())
BEGIN (implicit)
...
CREATE TABLE t1 (
name VARCHAR(50) NOT NULL,
PRIMARY KEY (name)
)
...
INSERT INTO t1 (name) VALUES (?)
[...] [('some name 1',), ('some name 2',)]
COMMIT
BEGIN (implicit)
SELECT t1.name
FROM t1
WHERE t1.name = ?
[...] ('some name 1',)
[('some name 1',)]
ROLLBACK
Above, the AsyncConnection.run_sync() method may be used to
invoke special DDL functions such as MetaData.create_all() that
don’t include an awaitable hook.
Tip
It’s advisable to invoke the AsyncEngine.dispose() method
using await when using the AsyncEngine object in a
scope that will go out of context and be garbage collected, as illustrated in the
async_main function in the above example. This ensures that any
connections held open by the connection pool will be properly disposed
within an awaitable context. Unlike when using blocking IO, SQLAlchemy
cannot properly dispose of these connections within methods like __del__
or weakref finalizers as there is no opportunity to invoke await.
Failing to explicitly dispose of the engine when it falls out of scope
may result in warnings emitted to standard out resembling the form
RuntimeError: Event loop is closed within garbage collection.
The AsyncConnection also features a “streaming” API via
the AsyncConnection.stream() method that returns an
AsyncResult object. This result object uses a server-side
cursor and provides an async/await API, such as an async iterator:
async with engine.connect() as conn:
async_result = await conn.stream(select(t1))
async for row in async_result:
print("row: %s" % (row,))Synopsis - ORM¶
Using 2.0 style querying, the AsyncSession class
provides full ORM functionality.
Within the default mode of use, special care must be taken to avoid lazy loading or other expired-attribute access involving ORM relationships and column attributes; the next section Preventing Implicit IO when Using AsyncSession details this.
Warning
A single instance of AsyncSession is not safe for
use in multiple, concurrent tasks. See the sections
Using AsyncSession with Concurrent Tasks and Is the Session thread-safe? Is AsyncSession safe to share in concurrent tasks? for background.
The example below illustrates a complete example including mapper and session configuration:
>>> from __future__ import annotations
>>> import asyncio
>>> import datetime
>>> from typing import List
>>> from sqlalchemy import ForeignKey
>>> from sqlalchemy import func
>>> from sqlalchemy import select
>>> from sqlalchemy.ext.asyncio import AsyncAttrs
>>> from sqlalchemy.ext.asyncio import async_sessionmaker
>>> from sqlalchemy.ext.asyncio import AsyncSession
>>> from sqlalchemy.ext.asyncio import create_async_engine
>>> from sqlalchemy.orm import DeclarativeBase
>>> from sqlalchemy.orm import Mapped
>>> from sqlalchemy.orm import mapped_column
>>> from sqlalchemy.orm import relationship
>>> from sqlalchemy.orm import selectinload
>>> class Base(AsyncAttrs, DeclarativeBase):
... pass
>>> class B(Base):
... __tablename__ = "b"
...
... id: Mapped[int] = mapped_column(primary_key=True)
... a_id: Mapped[int] = mapped_column(ForeignKey("a.id"))
... data: Mapped[str]
>>> class A(Base):
... __tablename__ = "a"
...
... id: Mapped[int] = mapped_column(primary_key=True)
... data: Mapped[str]
... create_date: Mapped[datetime.datetime] = mapped_column(server_default=func.now())
... bs: Mapped[List[B]] = relationship()
>>> async def insert_objects(async_session: async_sessionmaker[AsyncSession]) -> None:
... async with async_session() as session:
... async with session.begin():
... session.add_all(
... [
... A(bs=[B(data="b1"), B(data="b2")], data="a1"),
... A(bs=[], data="a2"),
... A(bs=[B(data="b3"), B(data="b4")], data="a3"),
... ]
... )
>>> async def select_and_update_objects(
... async_session: async_sessionmaker[AsyncSession],
... ) -> None:
... async with async_session() as session:
... stmt = select(A).order_by(A.id).options(selectinload(A.bs))
...
... result = await session.execute(stmt)
...
... for a in result.scalars():
... print(a, a.data)
... print(f"created at: {a.create_date}")
... for b in a.bs:
... print(b, b.data)
...
... result = await session.execute(select(A).order_by(A.id).limit(1))
...
... a1 = result.scalars().one()
...
... a1.data = "new data"
...
... await session.commit()
...
... # access attribute subsequent to commit; this is what
... # expire_on_commit=False allows
... print(a1.data)
...
... # alternatively, AsyncAttrs may be used to access any attribute
... # as an awaitable (new in 2.0.13)
... for b1 in await a1.awaitable_attrs.bs:
... print(b1, b1.data)
>>> async def async_main() -> None:
... engine = create_async_engine("sqlite+aiosqlite://", echo=True)
...
... # async_sessionmaker: a factory for new AsyncSession objects.
... # expire_on_commit - don't expire objects after transaction commit
... async_session = async_sessionmaker(engine, expire_on_commit=False)
...
... async with engine.begin() as conn:
... await conn.run_sync(Base.metadata.create_all)
...
... await insert_objects(async_session)
... await select_and_update_objects(async_session)
...
... # for AsyncEngine created in function scope, close and
... # clean-up pooled connections
... await engine.dispose()
>>> asyncio.run(async_main())
BEGIN (implicit)
...
CREATE TABLE a (
id INTEGER NOT NULL,
data VARCHAR NOT NULL,
create_date DATETIME DEFAULT (CURRENT_TIMESTAMP) NOT NULL,
PRIMARY KEY (id)
)
...
CREATE TABLE b (
id INTEGER NOT NULL,
a_id INTEGER NOT NULL,
data VARCHAR NOT NULL,
PRIMARY KEY (id),
FOREIGN KEY(a_id) REFERENCES a (id)
)
...
COMMIT
BEGIN (implicit)
INSERT INTO a (data) VALUES (?) RETURNING id, create_date
[...] ('a1',)
...
INSERT INTO b (a_id, data) VALUES (?, ?) RETURNING id
[...] (1, 'b2')
...
COMMIT
BEGIN (implicit)
SELECT a.id, a.data, a.create_date
FROM a ORDER BY a.id
[...] ()
SELECT b.a_id AS b_a_id, b.id AS b_id, b.data AS b_data
FROM b
WHERE b.a_id IN (?, ?, ?)
[...] (1, 2, 3)
<A object at ...> a1
created at: ...
<B object at ...> b1
<B object at ...> b2
<A object at ...> a2
created at: ...
<A object at ...> a3
created at: ...
<B object at ...> b3
<B object at ...> b4
SELECT a.id, a.data, a.create_date
FROM a ORDER BY a.id
LIMIT ? OFFSET ?
[...] (1, 0)
UPDATE a SET data=? WHERE a.id = ?
[...] ('new data', 1)
COMMIT
new data
<B object at ...> b1
<B object at ...> b2
In the example above, the AsyncSession is instantiated using
the optional async_sessionmaker helper, which provides
a factory for new AsyncSession objects with a fixed set
of parameters, which here includes associating it with
an AsyncEngine against particular database URL. It is then
passed to other methods where it may be used in a Python asynchronous context
manager (i.e. async with: statement) so that it is automatically closed at
the end of the block; this is equivalent to calling the
AsyncSession.close() method.
Using AsyncSession with Concurrent Tasks¶
The AsyncSession object is a mutable, stateful object
which represents a single, stateful database transaction in progress. Using
concurrent tasks with asyncio, with APIs such as asyncio.gather() for
example, should use a separate AsyncSession per individual
task.
See the section Is the Session thread-safe? Is AsyncSession safe to share in concurrent tasks? for a general description of
the Session and AsyncSession with regards to
how they should be used with concurrent workloads.
Preventing Implicit IO when Using AsyncSession¶
Using traditional asyncio, the application needs to avoid any points at which IO-on-attribute access may occur. Techniques that can be used to help this are below, many of which are illustrated in the preceding example.
Attributes that are lazy-loading relationships, deferred columns or expressions, or are being accessed in expiration scenarios can take advantage of the
AsyncAttrsmixin. This mixin, when added to a specific class or more generally to the DeclarativeBasesuperclass, provides an accessorAsyncAttrs.awaitable_attrswhich delivers any attribute as an awaitable:from __future__ import annotations from typing import List from sqlalchemy.ext.asyncio import AsyncAttrs from sqlalchemy.orm import DeclarativeBase from sqlalchemy.orm import Mapped from sqlalchemy.orm import relationship class Base(AsyncAttrs, DeclarativeBase): pass class A(Base): __tablename__ = "a" # ... rest of mapping ... bs: Mapped[List[B]] = relationship() class B(Base): __tablename__ = "b" # ... rest of mapping ...
Accessing the
A.bscollection on newly loaded instances ofAwhen eager loading is not in use will normally use lazy loading, which in order to succeed will usually emit IO to the database, which will fail under asyncio as no implicit IO is allowed. To access this attribute directly under asyncio without any prior loading operations, the attribute can be accessed as an awaitable by indicating theAsyncAttrs.awaitable_attrsprefix:a1 = (await session.scalars(select(A))).one() for b1 in await a1.awaitable_attrs.bs: print(b1)
The
AsyncAttrsmixin provides a succinct facade over the internal approach that’s also used by theAsyncSession.run_sync()method.New in version 2.0.13.
See also
Collections can be replaced with write only collections that will never emit IO implicitly, by using the Write Only Relationships feature in SQLAlchemy 2.0. Using this feature, collections are never read from, only queried using explicit SQL calls. See the example
async_orm_writeonly.pyin the Asyncio Integration section for an example of write-only collections used with asyncio.When using write only collections, the program’s behavior is simple and easy to predict regarding collections. However, the downside is that there is not any built-in system for loading many of these collections all at once, which instead would need to be performed manually. Therefore, many of the bullets below address specific techniques when using traditional lazy-loaded relationships with asyncio, which requires more care.
If not using
AsyncAttrs, relationships can be declared withlazy="raise"so that by default they will not attempt to emit SQL. In order to load collections, eager loading would be used instead.The most useful eager loading strategy is the
selectinload()eager loader, which is employed in the previous example in order to eagerly load theA.bscollection within the scope of theawait session.execute()call:stmt = select(A).options(selectinload(A.bs))
When constructing new objects, collections are always assigned a default, empty collection, such as a list in the above example:
A(bs=[], data="a2")
This allows the
.bscollection on the aboveAobject to be present and readable when theAobject is flushed; otherwise, when theAis flushed,.bswould be unloaded and would raise an error on access.The
AsyncSessionis configured usingSession.expire_on_commitset to False, so that we may access attributes on an object subsequent to a call toAsyncSession.commit(), as in the line at the end where we access an attribute:# create AsyncSession with expire_on_commit=False async_session = AsyncSession(engine, expire_on_commit=False) # sessionmaker version async_session = async_sessionmaker(engine, expire_on_commit=False) async with async_session() as session: result = await session.execute(select(A).order_by(A.id)) a1 = result.scalars().first() # commit would normally expire all attributes await session.commit() # access attribute subsequent to commit; this is what # expire_on_commit=False allows print(a1.data)
Other guidelines include:
Methods like
AsyncSession.expire()should be avoided in favor ofAsyncSession.refresh(); if expiration is absolutely needed. Expiration should generally not be needed asSession.expire_on_commitshould normally be set toFalsewhen using asyncio.A lazy-loaded relationship can be loaded explicitly under asyncio using
AsyncSession.refresh(), if the desired attribute name is passed explicitly toSession.refresh.attribute_names, e.g.:# assume a_obj is an A that has lazy loaded A.bs collection a_obj = await async_session.get(A, [1]) # force the collection to load by naming it in attribute_names await async_session.refresh(a_obj, ["bs"]) # collection is present print(f"bs collection: {a_obj.bs}")
It’s of course preferable to use eager loading up front in order to have collections already set up without the need to lazy-load.
New in version 2.0.4: Added support for
AsyncSession.refresh()and the underlyingSession.refresh()method to force lazy-loaded relationships to load, if they are named explicitly in theSession.refresh.attribute_namesparameter. In previous versions, the relationship would be silently skipped even if named in the parameter.Avoid using the
allcascade option documented at Cascades in favor of listing out the desired cascade features explicitly. Theallcascade option implies among others the refresh-expire setting, which means that theAsyncSession.refresh()method will expire the attributes on related objects, but not necessarily refresh those related objects assuming eager loading is not configured within therelationship(), leaving them in an expired state.Appropriate loader options should be employed for
deferred()columns, if used at all, in addition to that ofrelationship()constructs as noted above. See Limiting which Columns Load with Column Deferral for background on deferred column loading.
The “dynamic” relationship loader strategy described at Dynamic Relationship Loaders is not compatible by default with the asyncio approach. It can be used directly only if invoked within the
AsyncSession.run_sync()method described at Running Synchronous Methods and Functions under asyncio, or by using its.statementattribute to obtain a normal select:user = await session.get(User, 42) addresses = (await session.scalars(user.addresses.statement)).all() stmt = user.addresses.statement.where(Address.email_address.startswith("patrick")) addresses_filter = (await session.scalars(stmt)).all()
The write only technique, introduced in version 2.0 of SQLAlchemy, is fully compatible with asyncio and should be preferred.
See also
“Dynamic” relationship loaders superseded by “Write Only” - notes on migration to 2.0 style
If using asyncio with a database that does not support RETURNING, such as MySQL 8, server default values such as generated timestamps will not be available on newly flushed objects unless the
Mapper.eager_defaultsoption is used. In SQLAlchemy 2.0, this behavior is applied automatically to backends like PostgreSQL, SQLite and MariaDB which use RETURNING to fetch new values when rows are INSERTed.
Running Synchronous Methods and Functions under asyncio¶
Deep Alchemy
This approach is essentially exposing publicly the
mechanism by which SQLAlchemy is able to provide the asyncio interface
in the first place. While there is no technical issue with doing so, overall
the approach can probably be considered “controversial” as it works against
some of the central philosophies of the asyncio programming model, which
is essentially that any programming statement that can potentially result
in IO being invoked must have an await call, lest the program
does not make it explicitly clear every line at which IO may occur.
This approach does not change that general idea, except that it allows
a series of synchronous IO instructions to be exempted from this rule
within the scope of a function call, essentially bundled up into a single
awaitable.
As an alternative means of integrating traditional SQLAlchemy “lazy loading”
within an asyncio event loop, an optional method known as
AsyncSession.run_sync() is provided which will run any
Python function inside of a greenlet, where traditional synchronous
programming concepts will be translated to use await when they reach the
database driver. A hypothetical approach here is an asyncio-oriented
application can package up database-related methods into functions that are
invoked using AsyncSession.run_sync().
Altering the above example, if we didn’t use selectinload()
for the A.bs collection, we could accomplish our treatment of these
attribute accesses within a separate function:
import asyncio
from sqlalchemy import select
from sqlalchemy.ext.asyncio import AsyncSession, create_async_engine
def fetch_and_update_objects(session):
"""run traditional sync-style ORM code in a function that will be
invoked within an awaitable.
"""
# the session object here is a traditional ORM Session.
# all features are available here including legacy Query use.
stmt = select(A)
result = session.execute(stmt)
for a1 in result.scalars():
print(a1)
# lazy loads
for b1 in a1.bs:
print(b1)
# legacy Query use
a1 = session.query(A).order_by(A.id).first()
a1.data = "new data"
async def async_main():
engine = create_async_engine(
"postgresql+asyncpg://scott:tiger@localhost/test",
echo=True,
)
async with engine.begin() as conn:
await conn.run_sync(Base.metadata.drop_all)
await conn.run_sync(Base.metadata.create_all)
async with AsyncSession(engine) as session:
async with session.begin():
session.add_all(
[
A(bs=[B(), B()], data="a1"),
A(bs=[B()], data="a2"),
A(bs=[B(), B()], data="a3"),
]
)
await session.run_sync(fetch_and_update_objects)
await session.commit()
# for AsyncEngine created in function scope, close and
# clean-up pooled connections
await engine.dispose()
asyncio.run(async_main())The above approach of running certain functions within a “sync” runner
has some parallels to an application that runs a SQLAlchemy application
on top of an event-based programming library such as gevent. The
differences are as follows:
unlike when using
gevent, we can continue to use the standard Python asyncio event loop, or any custom event loop, without the need to integrate into thegeventevent loop.There is no “monkeypatching” whatsoever. The above example makes use of a real asyncio driver and the underlying SQLAlchemy connection pool is also using the Python built-in
asyncio.Queuefor pooling connections.The program can freely switch between async/await code and contained functions that use sync code with virtually no performance penalty. There is no “thread executor” or any additional waiters or synchronization in use.
The underlying network drivers are also using pure Python asyncio concepts, no third party networking libraries as
geventandeventletprovides are in use.
Using events with the asyncio extension¶
The SQLAlchemy event system is not directly exposed by the asyncio extension, meaning there is not yet an “async” version of a SQLAlchemy event handler.
However, as the asyncio extension surrounds the usual synchronous SQLAlchemy API, regular “synchronous” style event handlers are freely available as they would be if asyncio were not used.
As detailed below, there are two current strategies to register events given asyncio-facing APIs:
Events can be registered at the instance level (e.g. a specific
AsyncEngineinstance) by associating the event with thesyncattribute that refers to the proxied object. For example to register thePoolEvents.connect()event against anAsyncEngineinstance, use itsAsyncEngine.sync_engineattribute as target. Targets include:To register an event at the class level, targeting all instances of the same type (e.g. all
AsyncSessioninstances), use the corresponding sync-style class. For example to register theSessionEvents.before_commit()event against theAsyncSessionclass, use theSessionclass as the target.To register at the
sessionmakerlevel, combine an explicitsessionmakerwith anasync_sessionmakerusingasync_sessionmaker.sync_session_class, and associate events with thesessionmaker.
When working within an event handler that is within an asyncio context, objects
like the Connection continue to work in their usual
“synchronous” way without requiring await or async usage; when messages
are ultimately received by the asyncio database adapter, the calling style is
transparently adapted back into the asyncio calling style. For events that
are passed a DBAPI level connection, such as PoolEvents.connect(),
the object is a pep-249 compliant “connection” object which will adapt
sync-style calls into the asyncio driver.
Examples of Event Listeners with Async Engines / Sessions / Sessionmakers¶
Some examples of sync style event handlers associated with async-facing API constructs are illustrated below:
Core Events on AsyncEngine
In this example, we access the
AsyncEngine.sync_engineattribute ofAsyncEngineas the target forConnectionEventsandPoolEvents:import asyncio from sqlalchemy import event from sqlalchemy import text from sqlalchemy.engine import Engine from sqlalchemy.ext.asyncio import create_async_engine engine = create_async_engine("postgresql+asyncpg://scott:tiger@localhost:5432/test") # connect event on instance of Engine @event.listens_for(engine.sync_engine, "connect") def my_on_connect(dbapi_con, connection_record): print("New DBAPI connection:", dbapi_con) cursor = dbapi_con.cursor() # sync style API use for adapted DBAPI connection / cursor cursor.execute("select 'execute from event'") print(cursor.fetchone()[0]) # before_execute event on all Engine instances @event.listens_for(Engine, "before_execute") def my_before_execute( conn, clauseelement, multiparams, params, execution_options, ): print("before execute!") async def go(): async with engine.connect() as conn: await conn.execute(text("select 1")) await engine.dispose() asyncio.run(go())
Output:
New DBAPI connection: <AdaptedConnection <asyncpg.connection.Connection object at 0x7f33f9b16960>> execute from event before execute!
ORM Events on AsyncSession
In this example, we access
AsyncSession.sync_sessionas the target forSessionEvents:import asyncio from sqlalchemy import event from sqlalchemy import text from sqlalchemy.ext.asyncio import AsyncSession from sqlalchemy.ext.asyncio import create_async_engine from sqlalchemy.orm import Session engine = create_async_engine("postgresql+asyncpg://scott:tiger@localhost:5432/test") session = AsyncSession(engine) # before_commit event on instance of Session @event.listens_for(session.sync_session, "before_commit") def my_before_commit(session): print("before commit!") # sync style API use on Session connection = session.connection() # sync style API use on Connection result = connection.execute(text("select 'execute from event'")) print(result.first()) # after_commit event on all Session instances @event.listens_for(Session, "after_commit") def my_after_commit(session): print("after commit!") async def go(): await session.execute(text("select 1")) await session.commit() await session.close() await engine.dispose() asyncio.run(go())
Output:
before commit! execute from event after commit!
ORM Events on async_sessionmaker
For this use case, we make a
sessionmakeras the event target, then assign it to theasync_sessionmakerusing theasync_sessionmaker.sync_session_classparameter:import asyncio from sqlalchemy import event from sqlalchemy.ext.asyncio import async_sessionmaker from sqlalchemy.orm import sessionmaker sync_maker = sessionmaker() maker = async_sessionmaker(sync_session_class=sync_maker) @event.listens_for(sync_maker, "before_commit") def before_commit(session): print("before commit") async def main(): async_session = maker() await async_session.commit() asyncio.run(main())
Output:
before commit
Using awaitable-only driver methods in connection pool and other events¶
As discussed in the above section, event handlers such as those oriented
around the PoolEvents event handlers receive a sync-style “DBAPI” connection,
which is a wrapper object supplied by SQLAlchemy asyncio dialects to adapt
the underlying asyncio “driver” connection into one that can be used by
SQLAlchemy’s internals. A special use case arises when the user-defined
implementation for such an event handler needs to make use of the
ultimate “driver” connection directly, using awaitable only methods on that
driver connection. One such example is the .set_type_codec() method
supplied by the asyncpg driver.
To accommodate this use case, SQLAlchemy’s AdaptedConnection
class provides a method AdaptedConnection.run_async() that allows
an awaitable function to be invoked within the “synchronous” context of
an event handler or other SQLAlchemy internal. This method is directly
analogous to the AsyncConnection.run_sync() method that
allows a sync-style method to run under async.
AdaptedConnection.run_async() should be passed a function that will
accept the innermost “driver” connection as a single argument, and return
an awaitable that will be invoked by the AdaptedConnection.run_async()
method. The given function itself does not need to be declared as async;
it’s perfectly fine for it to be a Python lambda:, as the return awaitable
value will be invoked after being returned:
from sqlalchemy import event
from sqlalchemy.ext.asyncio import create_async_engine
engine = create_async_engine(...)
@event.listens_for(engine.sync_engine, "connect")
def register_custom_types(dbapi_connection, *args):
dbapi_connection.run_async(
lambda connection: connection.set_type_codec(
"MyCustomType",
encoder,
decoder, # ...
)
)Above, the object passed to the register_custom_types event handler
is an instance of AdaptedConnection, which provides a DBAPI-like
interface to an underlying async-only driver-level connection object.
The AdaptedConnection.run_async() method then provides access to an
awaitable environment where the underlying driver level connection may be
acted upon.
New in version 1.4.30.
Using multiple asyncio event loops¶
An application that makes use of multiple event loops, for example in the
uncommon case of combining asyncio with multithreading, should not share the
same AsyncEngine with different event loops when using the
default pool implementation.
If an AsyncEngine is be passed from one event loop to another,
the method AsyncEngine.dispose() should be called before it’s
re-used on a new event loop. Failing to do so may lead to a RuntimeError
along the lines of
Task <Task pending ...> got Future attached to a different loop
If the same engine must be shared between different loop, it should be configured
to disable pooling using NullPool, preventing the Engine
from using any connection more than once:
from sqlalchemy.ext.asyncio import create_async_engine
from sqlalchemy.pool import NullPool
engine = create_async_engine(
"postgresql+asyncpg://user:pass@host/dbname",
poolclass=NullPool,
)Using asyncio scoped session¶
The “scoped session” pattern used in threaded SQLAlchemy with the
scoped_session object is also available in asyncio, using
an adapted version called async_scoped_session.
Tip
SQLAlchemy generally does not recommend the “scoped” pattern
for new development as it relies upon mutable global state that must also be
explicitly torn down when work within the thread or task is complete.
Particularly when using asyncio, it’s likely a better idea to pass the
AsyncSession directly to the awaitable functions that need
it.
When using async_scoped_session, as there’s no “thread-local”
concept in the asyncio context, the “scopefunc” parameter must be provided to
the constructor. The example below illustrates using the
asyncio.current_task() function for this purpose:
from asyncio import current_task
from sqlalchemy.ext.asyncio import (
async_scoped_session,
async_sessionmaker,
)
async_session_factory = async_sessionmaker(
some_async_engine,
expire_on_commit=False,
)
AsyncScopedSession = async_scoped_session(
async_session_factory,
scopefunc=current_task,
)
some_async_session = AsyncScopedSession()Warning
The “scopefunc” used by async_scoped_session
is invoked an arbitrary number of times within a task, once for each
time the underlying AsyncSession is accessed. The function
should therefore be idempotent and lightweight, and should not attempt
to create or mutate any state, such as establishing callbacks, etc.
Warning
Using current_task() for the “key” in the scope requires that
the async_scoped_session.remove() method is called from
within the outermost awaitable, to ensure the key is removed from the
registry when the task is complete, otherwise the task handle as well as
the AsyncSession will remain in memory, essentially
creating a memory leak. See the following example which illustrates
the correct use of async_scoped_session.remove().
async_scoped_session includes proxy
behavior similar to that of scoped_session, which means it can be
treated as a AsyncSession directly, keeping in mind that
the usual await keywords are necessary, including for the
async_scoped_session.remove() method:
async def some_function(some_async_session, some_object):
# use the AsyncSession directly
some_async_session.add(some_object)
# use the AsyncSession via the context-local proxy
await AsyncScopedSession.commit()
# "remove" the current proxied AsyncSession for the local context
await AsyncScopedSession.remove()New in version 1.4.19.
Using the Inspector to inspect schema objects¶
SQLAlchemy does not yet offer an asyncio version of the
Inspector (introduced at Fine Grained Reflection with Inspector),
however the existing interface may be used in an asyncio context by
leveraging the AsyncConnection.run_sync() method of
AsyncConnection:
import asyncio
from sqlalchemy import inspect
from sqlalchemy.ext.asyncio import create_async_engine
engine = create_async_engine("postgresql+asyncpg://scott:tiger@localhost/test")
def use_inspector(conn):
inspector = inspect(conn)
# use the inspector
print(inspector.get_view_names())
# return any value to the caller
return inspector.get_table_names()
async def async_main():
async with engine.connect() as conn:
tables = await conn.run_sync(use_inspector)
asyncio.run(async_main())Engine API Documentation¶
| Object Name | Description |
|---|---|
async_engine_from_config(configuration[, prefix], **kwargs) |
Create a new AsyncEngine instance using a configuration dictionary. |
An asyncio proxy for a |
|
An asyncio proxy for a |
|
An asyncio proxy for a |
|
create_async_engine(url, **kw) |
Create a new async engine instance. |
create_async_pool_from_url(url, **kwargs) |
Create a new async engine instance. |
- function sqlalchemy.ext.asyncio.create_async_engine(url: str | URL, **kw: Any) AsyncEngine¶
Create a new async engine instance.
Arguments passed to
create_async_engine()are mostly identical to those passed to thecreate_engine()function. The specified dialect must be an asyncio-compatible dialect such as asyncpg.New in version 1.4.
- Parameters:
async_creator¶ –
an async callable which returns a driver-level asyncio connection. If given, the function should take no arguments, and return a new asyncio connection from the underlying asyncio database driver; the connection will be wrapped in the appropriate structures to be used with the
AsyncEngine. Note that the parameters specified in the URL are not applied here, and the creator function should use its own connection parameters.This parameter is the asyncio equivalent of the
create_engine.creatorparameter of thecreate_engine()function.New in version 2.0.16.
- function sqlalchemy.ext.asyncio.async_engine_from_config(configuration: Dict[str, Any], prefix: str = 'sqlalchemy.', **kwargs: Any) AsyncEngine¶
Create a new AsyncEngine instance using a configuration dictionary.
This function is analogous to the
engine_from_config()function in SQLAlchemy Core, except that the requested dialect must be an asyncio-compatible dialect such as asyncpg. The argument signature of the function is identical to that ofengine_from_config().New in version 1.4.29.
- function sqlalchemy.ext.asyncio.create_async_pool_from_url(url: str | URL, **kwargs: Any) Pool¶
Create a new async engine instance.
Arguments passed to
create_async_pool_from_url()are mostly identical to those passed to thecreate_pool_from_url()function. The specified dialect must be an asyncio-compatible dialect such as asyncpg.New in version 2.0.10.
- class sqlalchemy.ext.asyncio.AsyncEngine¶
An asyncio proxy for a
Engine.AsyncEngineis acquired using thecreate_async_engine()function:from sqlalchemy.ext.asyncio import create_async_engine engine = create_async_engine("postgresql+asyncpg://user:pass@host/dbname")
New in version 1.4.
Members
begin(), clear_compiled_cache(), connect(), dialect, dispose(), driver, echo, engine, execution_options(), get_execution_options(), name, pool, raw_connection(), sync_engine, update_execution_options(), url
Class signature
class
sqlalchemy.ext.asyncio.AsyncEngine(sqlalchemy.ext.asyncio.base.ProxyComparable,sqlalchemy.ext.asyncio.AsyncConnectable)-
method
sqlalchemy.ext.asyncio.AsyncEngine.begin() AsyncIterator[AsyncConnection]¶ Return a context manager which when entered will deliver an
AsyncConnectionwith anAsyncTransactionestablished.E.g.:
async with async_engine.begin() as conn: await conn.execute( text("insert into table (x, y, z) values (1, 2, 3)") ) await conn.execute(text("my_special_procedure(5)"))
-
method
sqlalchemy.ext.asyncio.AsyncEngine.clear_compiled_cache() None¶ Clear the compiled cache associated with the dialect.
Proxied for the
Engineclass on behalf of theAsyncEngineclass.This applies only to the built-in cache that is established via the
create_engine.query_cache_sizeparameter. It will not impact any dictionary caches that were passed via theConnection.execution_options.compiled_cacheparameter.New in version 1.4.
-
method
sqlalchemy.ext.asyncio.AsyncEngine.connect() AsyncConnection¶ Return an
AsyncConnectionobject.The
AsyncConnectionwill procure a database connection from the underlying connection pool when it is entered as an async context manager:async with async_engine.connect() as conn: result = await conn.execute(select(user_table))
The
AsyncConnectionmay also be started outside of a context manager by invoking itsAsyncConnection.start()method.
-
attribute
sqlalchemy.ext.asyncio.AsyncEngine.dialect¶ Proxy for the
Engine.dialectattribute on behalf of theAsyncEngineclass.
-
method
sqlalchemy.ext.asyncio.AsyncEngine.async dispose(close: bool = True) None¶ Dispose of the connection pool used by this
AsyncEngine.- Parameters:
close¶ –
if left at its default of
True, has the effect of fully closing all currently checked in database connections. Connections that are still checked out will not be closed, however they will no longer be associated with thisEngine, so when they are closed individually, eventually thePoolwhich they are associated with will be garbage collected and they will be closed out fully, if not already closed on checkin.If set to
False, the previous connection pool is de-referenced, and otherwise not touched in any way.
See also
-
attribute
sqlalchemy.ext.asyncio.AsyncEngine.driver¶ Driver name of the
Dialectin use by thisEngine.Proxied for the
Engineclass on behalf of theAsyncEngineclass.
-
attribute
sqlalchemy.ext.asyncio.AsyncEngine.echo¶ When
True, enable log output for this element.Proxied for the
Engineclass on behalf of theAsyncEngineclass.This has the effect of setting the Python logging level for the namespace of this element’s class and object reference. A value of boolean
Trueindicates that the loglevellogging.INFOwill be set for the logger, whereas the string valuedebugwill set the loglevel tologging.DEBUG.
-
attribute
sqlalchemy.ext.asyncio.AsyncEngine.engine¶ Returns this
Engine.Proxied for the
Engineclass on behalf of theAsyncEngineclass.Used for legacy schemes that accept
Connection/Engineobjects within the same variable.
-
method
sqlalchemy.ext.asyncio.AsyncEngine.execution_options(**opt: Any) AsyncEngine¶ Return a new
AsyncEnginethat will provideAsyncConnectionobjects with the given execution options.Proxied from
Engine.execution_options(). See that method for details.
-
method
sqlalchemy.ext.asyncio.AsyncEngine.get_execution_options() _ExecuteOptions¶ Get the non-SQL options which will take effect during execution.
Proxied for the
Engineclass on behalf of theAsyncEngineclass.See also
-
attribute
sqlalchemy.ext.asyncio.AsyncEngine.name¶ String name of the
Dialectin use by thisEngine.Proxied for the
Engineclass on behalf of theAsyncEngineclass.
-
attribute
sqlalchemy.ext.asyncio.AsyncEngine.pool¶ Proxy for the
Engine.poolattribute on behalf of theAsyncEngineclass.
-
method
sqlalchemy.ext.asyncio.AsyncEngine.async raw_connection() PoolProxiedConnection¶ Return a “raw” DBAPI connection from the connection pool.
-
attribute
sqlalchemy.ext.asyncio.AsyncEngine.sync_engine: Engine¶ Reference to the sync-style
EnginethisAsyncEngineproxies requests towards.This instance can be used as an event target.
-
method
sqlalchemy.ext.asyncio.AsyncEngine.update_execution_options(**opt: Any) None¶ Update the default execution_options dictionary of this
Engine.Proxied for the
Engineclass on behalf of theAsyncEngineclass.The given keys/values in **opt are added to the default execution options that will be used for all connections. The initial contents of this dictionary can be sent via the
execution_optionsparameter tocreate_engine().
-
attribute
sqlalchemy.ext.asyncio.AsyncEngine.url¶ Proxy for the
Engine.urlattribute on behalf of theAsyncEngineclass.
-
method
- class sqlalchemy.ext.asyncio.AsyncConnection¶
An asyncio proxy for a
Connection.AsyncConnectionis acquired using theAsyncEngine.connect()method ofAsyncEngine:from sqlalchemy.ext.asyncio import create_async_engine engine = create_async_engine("postgresql+asyncpg://user:pass@host/dbname") async with engine.connect() as conn: result = await conn.execute(select(table))
New in version 1.4.
Members
aclose(), begin(), begin_nested(), close(), closed, commit(), connection, default_isolation_level, dialect, exec_driver_sql(), execute(), execution_options(), get_nested_transaction(), get_raw_connection(), get_transaction(), in_nested_transaction(), in_transaction(), info, invalidate(), invalidated, rollback(), run_sync(), scalar(), scalars(), start(), stream(), stream_scalars(), sync_connection, sync_engine
Class signature
class
sqlalchemy.ext.asyncio.AsyncConnection(sqlalchemy.ext.asyncio.base.ProxyComparable,sqlalchemy.ext.asyncio.base.StartableContext,sqlalchemy.ext.asyncio.AsyncConnectable)-
method
sqlalchemy.ext.asyncio.AsyncConnection.async aclose() None¶ A synonym for
AsyncConnection.close().The
AsyncConnection.aclose()name is specifically to support the Python standard library@contextlib.aclosingcontext manager function.New in version 2.0.20.
-
method
sqlalchemy.ext.asyncio.AsyncConnection.begin() AsyncTransaction¶ Begin a transaction prior to autobegin occurring.
-
method
sqlalchemy.ext.asyncio.AsyncConnection.begin_nested() AsyncTransaction¶ Begin a nested transaction and return a transaction handle.
-
method
sqlalchemy.ext.asyncio.AsyncConnection.async close() None¶ Close this
AsyncConnection.This has the effect of also rolling back the transaction if one is in place.
-
attribute
sqlalchemy.ext.asyncio.AsyncConnection.closed¶ Return True if this connection is closed.
Proxied for the
Connectionclass on behalf of theAsyncConnectionclass.
-
method
sqlalchemy.ext.asyncio.AsyncConnection.async commit() None¶ Commit the transaction that is currently in progress.
This method commits the current transaction if one has been started. If no transaction was started, the method has no effect, assuming the connection is in a non-invalidated state.
A transaction is begun on a
Connectionautomatically whenever a statement is first executed, or when theConnection.begin()method is called.
-
attribute
sqlalchemy.ext.asyncio.AsyncConnection.connection¶ Not implemented for async; call
AsyncConnection.get_raw_connection().
-
attribute
sqlalchemy.ext.asyncio.AsyncConnection.default_isolation_level¶ The initial-connection time isolation level associated with the
Dialectin use.Proxied for the
Connectionclass on behalf of theAsyncConnectionclass.This value is independent of the
Connection.execution_options.isolation_levelandEngine.execution_options.isolation_levelexecution options, and is determined by theDialectwhen the first connection is created, by performing a SQL query against the database for the current isolation level before any additional commands have been emitted.Calling this accessor does not invoke any new SQL queries.
See also
Connection.get_isolation_level()- view current actual isolation levelcreate_engine.isolation_level- set perEngineisolation levelConnection.execution_options.isolation_level- set perConnectionisolation level
-
attribute
sqlalchemy.ext.asyncio.AsyncConnection.dialect¶ Proxy for the
Connection.dialectattribute on behalf of theAsyncConnectionclass.
-
method
sqlalchemy.ext.asyncio.AsyncConnection.async exec_driver_sql(statement: str, parameters: _DBAPIAnyExecuteParams | None = None, execution_options: CoreExecuteOptionsParameter | None = None) CursorResult[Any]¶ Executes a driver-level SQL string and return buffered
Result.
-
method
sqlalchemy.ext.asyncio.AsyncConnection.async execute(statement: Executable, parameters: _CoreAnyExecuteParams | None = None, *, execution_options: CoreExecuteOptionsParameter | None = None) CursorResult[Any]¶ Executes a SQL statement construct and return a buffered
Result.- Parameters:
object¶ –
The statement to be executed. This is always an object that is in both the
ClauseElementandExecutablehierarchies, including:DDLand objects which inherit fromExecutableDDLElement
parameters¶ – parameters which will be bound into the statement. This may be either a dictionary of parameter names to values, or a mutable sequence (e.g. a list) of dictionaries. When a list of dictionaries is passed, the underlying statement execution will make use of the DBAPI
cursor.executemany()method. When a single dictionary is passed, the DBAPIcursor.execute()method will be used.execution_options¶ – optional dictionary of execution options, which will be associated with the statement execution. This dictionary can provide a subset of the options that are accepted by
Connection.execution_options().
- Returns:
a
Resultobject.
-
method
sqlalchemy.ext.asyncio.AsyncConnection.async execution_options(**opt: Any) AsyncConnection¶ Set non-SQL options for the connection which take effect during execution.
This returns this
AsyncConnectionobject with the new options added.See
Connection.execution_options()for full details on this method.
-
method
sqlalchemy.ext.asyncio.AsyncConnection.get_nested_transaction() AsyncTransaction | None¶ Return an
AsyncTransactionrepresenting the current nested (savepoint) transaction, if any.This makes use of the underlying synchronous connection’s
Connection.get_nested_transaction()method to get the currentTransaction, which is then proxied in a newAsyncTransactionobject.New in version 1.4.0b2.
-
method
sqlalchemy.ext.asyncio.AsyncConnection.async get_raw_connection() PoolProxiedConnection¶ Return the pooled DBAPI-level connection in use by this
AsyncConnection.This is a SQLAlchemy connection-pool proxied connection which then has the attribute
_ConnectionFairy.driver_connectionthat refers to the actual driver connection. Its_ConnectionFairy.dbapi_connectionrefers instead to anAdaptedConnectioninstance that adapts the driver connection to the DBAPI protocol.
-
method
sqlalchemy.ext.asyncio.AsyncConnection.get_transaction() AsyncTransaction | None¶ Return an
AsyncTransactionrepresenting the current transaction, if any.This makes use of the underlying synchronous connection’s
Connection.get_transaction()method to get the currentTransaction, which is then proxied in a newAsyncTransactionobject.New in version 1.4.0b2.
-
method
sqlalchemy.ext.asyncio.AsyncConnection.in_nested_transaction() bool¶ Return True if a transaction is in progress.
New in version 1.4.0b2.
-
method
sqlalchemy.ext.asyncio.AsyncConnection.in_transaction() bool¶ Return True if a transaction is in progress.
-
attribute
sqlalchemy.ext.asyncio.AsyncConnection.info¶ Return the
Connection.infodictionary of the underlyingConnection.This dictionary is freely writable for user-defined state to be associated with the database connection.
This attribute is only available if the
AsyncConnectionis currently connected. If theAsyncConnection.closedattribute isTrue, then accessing this attribute will raiseResourceClosedError.New in version 1.4.0b2.
-
method
sqlalchemy.ext.asyncio.AsyncConnection.async invalidate(exception: BaseException | None = None) None¶ Invalidate the underlying DBAPI connection associated with this
Connection.See the method
Connection.invalidate()for full detail on this method.
-
attribute
sqlalchemy.ext.asyncio.AsyncConnection.invalidated¶ Return True if this connection was invalidated.
Proxied for the
Connectionclass on behalf of theAsyncConnectionclass.This does not indicate whether or not the connection was invalidated at the pool level, however
-
method
sqlalchemy.ext.asyncio.AsyncConnection.async rollback() None¶ Roll back the transaction that is currently in progress.
This method rolls back the current transaction if one has been started. If no transaction was started, the method has no effect. If a transaction was started and the connection is in an invalidated state, the transaction is cleared using this method.
A transaction is begun on a
Connectionautomatically whenever a statement is first executed, or when theConnection.begin()method is called.
-
method
sqlalchemy.ext.asyncio.AsyncConnection.async run_sync(fn: ~typing.Callable[[~typing.Concatenate[~sqlalchemy.engine.base.Connection, ~_P]], ~sqlalchemy.ext.asyncio.engine._T], *arg: ~typing.~_P, **kw: ~typing.~_P) _T¶ Invoke the given synchronous (i.e. not async) callable, passing a synchronous-style
Connectionas the first argument.This method allows traditional synchronous SQLAlchemy functions to run within the context of an asyncio application.
E.g.:
def do_something_with_core(conn: Connection, arg1: int, arg2: str) -> str: '''A synchronous function that does not require awaiting :param conn: a Core SQLAlchemy Connection, used synchronously :return: an optional return value is supported ''' conn.execute( some_table.insert().values(int_col=arg1, str_col=arg2) ) return "success" async def do_something_async(async_engine: AsyncEngine) -> None: '''an async function that uses awaiting''' async with async_engine.begin() as async_conn: # run do_something_with_core() with a sync-style # Connection, proxied into an awaitable return_code = await async_conn.run_sync(do_something_with_core, 5, "strval") print(return_code)
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.
The most rudimentary use of
AsyncConnection.run_sync()is to invoke methods such asMetaData.create_all(), given anAsyncConnectionthat needs to be provided toMetaData.create_all()as aConnectionobject:# run metadata.create_all(conn) with a sync-style Connection, # proxied into an awaitable with async_engine.begin() as conn: await conn.run_sync(metadata.create_all)
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.
-
method
sqlalchemy.ext.asyncio.AsyncConnection.async scalar(statement: Executable, parameters: _CoreSingleExecuteParams | None = None, *, execution_options: CoreExecuteOptionsParameter | None = None) Any¶ Executes a SQL statement construct and returns a scalar object.
This method is shorthand for invoking the
Result.scalar()method after invoking theConnection.execute()method. Parameters are equivalent.- Returns:
a scalar Python value representing the first column of the first row returned.
-
method
sqlalchemy.ext.asyncio.AsyncConnection.async scalars(statement: Executable, parameters: _CoreAnyExecuteParams | None = None, *, execution_options: CoreExecuteOptionsParameter | None = None) ScalarResult[Any]¶ Executes a SQL statement construct and returns a scalar objects.
This method is shorthand for invoking the
Result.scalars()method after invoking theConnection.execute()method. Parameters are equivalent.- Returns:
a
ScalarResultobject.
New in version 1.4.24.
-
method
sqlalchemy.ext.asyncio.AsyncConnection.async start(is_ctxmanager: bool = False) AsyncConnection¶ Start this
AsyncConnectionobject’s context outside of using a Pythonwith:block.
-
method
sqlalchemy.ext.asyncio.AsyncConnection.stream(statement: Executable, parameters: _CoreAnyExecuteParams | None = None, *, execution_options: CoreExecuteOptionsParameter | None = None) AsyncIterator[AsyncResult[Any]]¶ Execute a statement and return an awaitable yielding a
AsyncResultobject.E.g.:
result = await conn.stream(stmt): async for row in result: print(f"{row}")
The
AsyncConnection.stream()method supports optional context manager use against theAsyncResultobject, as in:async with conn.stream(stmt) as result: async for row in result: print(f"{row}")
In the above pattern, the
AsyncResult.close()method is invoked unconditionally, even if the iterator is interrupted by an exception throw. Context manager use remains optional, however, and the function may be called in either anasync with fn():orawait fn()style.New in version 2.0.0b3: added context manager support
- Returns:
an awaitable object that will yield an
AsyncResultobject.
See also
-
method
sqlalchemy.ext.asyncio.AsyncConnection.stream_scalars(statement: Executable, parameters: _CoreSingleExecuteParams | None = None, *, execution_options: CoreExecuteOptionsParameter | None = None) AsyncIterator[AsyncScalarResult[Any]]¶ Execute a statement and return an awaitable yielding a
AsyncScalarResultobject.E.g.:
result = await conn.stream_scalars(stmt) async for scalar in result: print(f"{scalar}")
This method is shorthand for invoking the
AsyncResult.scalars()method after invoking theConnection.stream()method. Parameters are equivalent.The
AsyncConnection.stream_scalars()method supports optional context manager use against theAsyncScalarResultobject, as in:async with conn.stream_scalars(stmt) as result: async for scalar in result: print(f"{scalar}")
In the above pattern, the
AsyncScalarResult.close()method is invoked unconditionally, even if the iterator is interrupted by an exception throw. Context manager use remains optional, however, and the function may be called in either anasync with fn():orawait fn()style.New in version 2.0.0b3: added context manager support
- Returns:
an awaitable object that will yield an
AsyncScalarResultobject.
New in version 1.4.24.
See also
-
attribute
sqlalchemy.ext.asyncio.AsyncConnection.sync_connection: Connection | None¶ Reference to the sync-style
ConnectionthisAsyncConnectionproxies requests towards.This instance can be used as an event target.
-
attribute
sqlalchemy.ext.asyncio.AsyncConnection.sync_engine: Engine¶ Reference to the sync-style
EnginethisAsyncConnectionis associated with via its underlyingConnection.This instance can be used as an event target.
-
method
- class sqlalchemy.ext.asyncio.AsyncTransaction¶
An asyncio proxy for a
Transaction.Members
Class signature
class
sqlalchemy.ext.asyncio.AsyncTransaction(sqlalchemy.ext.asyncio.base.ProxyComparable,sqlalchemy.ext.asyncio.base.StartableContext)-
method
sqlalchemy.ext.asyncio.AsyncTransaction.async close() None¶ Close this
AsyncTransaction.If this transaction is the base transaction in a begin/commit nesting, the transaction will rollback(). Otherwise, the method returns.
This is used to cancel a Transaction without affecting the scope of an enclosing transaction.
-
method
sqlalchemy.ext.asyncio.AsyncTransaction.async commit() None¶ Commit this
AsyncTransaction.
-
method
sqlalchemy.ext.asyncio.AsyncTransaction.async rollback() None¶ Roll back this
AsyncTransaction.
-
method
sqlalchemy.ext.asyncio.AsyncTransaction.async start(is_ctxmanager: bool = False) AsyncTransaction¶ Start this
AsyncTransactionobject’s context outside of using a Pythonwith:block.
-
method
Result Set API Documentation¶
The AsyncResult object is an async-adapted version of the
Result object. It is only returned when using the
AsyncConnection.stream() or AsyncSession.stream()
methods, which return a result object that is on top of an active database
cursor.
| Object Name | Description |
|---|---|
A wrapper for a |
|
An asyncio wrapper around a |
|
A wrapper for a |
|
A |
- class sqlalchemy.ext.asyncio.AsyncResult¶
An asyncio wrapper around a
Resultobject.The
AsyncResultonly applies to statement executions that use a server-side cursor. It is returned only from theAsyncConnection.stream()andAsyncSession.stream()methods.Note
As is the case with
Result, this object is used for ORM results returned byAsyncSession.execute(), which can yield instances of ORM mapped objects either individually or within tuple-like rows. Note that these result objects do not deduplicate instances or rows automatically as is the case with the legacyQueryobject. For in-Python de-duplication of instances or rows, use theAsyncResult.unique()modifier method.New in version 1.4.
Members
all(), close(), closed, columns(), fetchall(), fetchmany(), fetchone(), first(), freeze(), keys(), mappings(), one(), one_or_none(), partitions(), scalar(), scalar_one(), scalar_one_or_none(), scalars(), t, tuples(), unique(), yield_per()
Class signature
class
sqlalchemy.ext.asyncio.AsyncResult(sqlalchemy.engine._WithKeys,sqlalchemy.ext.asyncio.AsyncCommon)-
method
sqlalchemy.ext.asyncio.AsyncResult.async all() Sequence[Row[_TP]]¶ Return all rows in a list.
Closes the result set after invocation. Subsequent invocations will return an empty list.
- Returns:
a list of
Rowobjects.
-
method
sqlalchemy.ext.asyncio.AsyncResult.async close() None¶ inherited from the
AsyncCommon.close()method ofAsyncCommonClose this result.
-
attribute
sqlalchemy.ext.asyncio.AsyncResult.closed¶ inherited from the
AsyncCommon.closedattribute ofAsyncCommonproxies the .closed attribute of the underlying result object, if any, else raises
AttributeError.New in version 2.0.0b3.
-
method
sqlalchemy.ext.asyncio.AsyncResult.columns(*col_expressions: _KeyIndexType) Self¶ Establish the columns that should be returned in each row.
Refer to
Result.columns()in the synchronous SQLAlchemy API for a complete behavioral description.
-
method
sqlalchemy.ext.asyncio.AsyncResult.async fetchall() Sequence[Row[_TP]]¶ A synonym for the
AsyncResult.all()method.New in version 2.0.
-
method
sqlalchemy.ext.asyncio.AsyncResult.async fetchmany(size: int | None = None) Sequence[Row[_TP]]¶ Fetch many rows.
When all rows are exhausted, returns an empty list.
This method is provided for backwards compatibility with SQLAlchemy 1.x.x.
To fetch rows in groups, use the
AsyncResult.partitions()method.- Returns:
a list of
Rowobjects.
See also
-
method
sqlalchemy.ext.asyncio.AsyncResult.async fetchone() Row[_TP] | None¶ Fetch one row.
When all rows are exhausted, returns None.
This method is provided for backwards compatibility with SQLAlchemy 1.x.x.
To fetch the first row of a result only, use the
AsyncResult.first()method. To iterate through all rows, iterate theAsyncResultobject directly.- Returns:
a
Rowobject if no filters are applied, orNoneif no rows remain.
-
method
sqlalchemy.ext.asyncio.AsyncResult.async first() Row[_TP] | None¶ Fetch the first row or
Noneif no row is present.Closes the result set and discards remaining rows.
Note
This method returns one row, e.g. tuple, by default. To return exactly one single scalar value, that is, the first column of the first row, use the
AsyncResult.scalar()method, or combineAsyncResult.scalars()andAsyncResult.first().Additionally, in contrast to the behavior of the legacy ORM
Query.first()method, no limit is applied to the SQL query which was invoked to produce thisAsyncResult; for a DBAPI driver that buffers results in memory before yielding rows, all rows will be sent to the Python process and all but the first row will be discarded.See also
- Returns:
a
Rowobject, or None if no rows remain.
-
method
sqlalchemy.ext.asyncio.AsyncResult.async freeze() FrozenResult[_TP]¶ Return a callable object that will produce copies of this
AsyncResultwhen invoked.The callable object returned is an instance of
FrozenResult.This is used for result set caching. The method must be called on the result when it has been unconsumed, and calling the method will consume the result fully. When the
FrozenResultis retrieved from a cache, it can be called any number of times where it will produce a newResultobject each time against its stored set of rows.See also
Re-Executing Statements - example usage within the ORM to implement a result-set cache.
-
method
sqlalchemy.ext.asyncio.AsyncResult.keys() RMKeyView¶ inherited from the
sqlalchemy.engine._WithKeys.keysmethod ofsqlalchemy.engine._WithKeysReturn an iterable view which yields the string keys that would be represented by each
Row.The keys can represent the labels of the columns returned by a core statement or the names of the orm classes returned by an orm execution.
The view also can be tested for key containment using the Python
inoperator, which will test both for the string keys represented in the view, as well as for alternate keys such as column objects.Changed in version 1.4: a key view object is returned rather than a plain list.
-
method
sqlalchemy.ext.asyncio.AsyncResult.mappings() AsyncMappingResult¶ Apply a mappings filter to returned rows, returning an instance of
AsyncMappingResult.When this filter is applied, fetching rows will return
RowMappingobjects instead ofRowobjects.- Returns:
a new
AsyncMappingResultfiltering object referring to the underlyingResultobject.
-
method
sqlalchemy.ext.asyncio.AsyncResult.async one() Row[_TP]¶ Return exactly one row or raise an exception.
Raises
NoResultFoundif the result returns no rows, orMultipleResultsFoundif multiple rows would be returned.Note
This method returns one row, e.g. tuple, by default. To return exactly one single scalar value, that is, the first column of the first row, use the
AsyncResult.scalar_one()method, or combineAsyncResult.scalars()andAsyncResult.one().New in version 1.4.
- Returns:
The first
Row.- Raises:
-
method
sqlalchemy.ext.asyncio.AsyncResult.async one_or_none() Row[_TP] | None¶ Return at most one result or raise an exception.
Returns
Noneif the result has no rows. RaisesMultipleResultsFoundif multiple rows are returned.New in version 1.4.
- Returns:
The first
RoworNoneif no row is available.- Raises:
-
method
sqlalchemy.ext.asyncio.AsyncResult.async partitions(size: int | None = None) AsyncIterator[Sequence[Row[_TP]]]¶ Iterate through sub-lists of rows of the size given.
An async iterator is returned:
async def scroll_results(connection): result = await connection.stream(select(users_table)) async for partition in result.partitions(100): print("list of rows: %s" % partition)
Refer to
Result.partitions()in the synchronous SQLAlchemy API for a complete behavioral description.
-
method
sqlalchemy.ext.asyncio.AsyncResult.async scalar() Any¶ Fetch the first column of the first row, and close the result set.
Returns
Noneif there are no rows to fetch.No validation is performed to test if additional rows remain.
After calling this method, the object is fully closed, e.g. the
CursorResult.close()method will have been called.- Returns:
a Python scalar value, or
Noneif no rows remain.
-
method
sqlalchemy.ext.asyncio.AsyncResult.async scalar_one() Any¶ Return exactly one scalar result or raise an exception.
This is equivalent to calling
AsyncResult.scalars()and thenAsyncScalarResult.one().
-
method
sqlalchemy.ext.asyncio.AsyncResult.async scalar_one_or_none() Any | None¶ Return exactly one scalar result or
None.This is equivalent to calling
AsyncResult.scalars()and thenAsyncScalarResult.one_or_none().
-
method
sqlalchemy.ext.asyncio.AsyncResult.scalars(index: _KeyIndexType = 0) AsyncScalarResult[Any]¶ Return an
AsyncScalarResultfiltering object which will return single elements rather thanRowobjects.Refer to
Result.scalars()in the synchronous SQLAlchemy API for a complete behavioral description.- Parameters:
index¶ – integer or row key indicating the column to be fetched from each row, defaults to
0indicating the first column.- Returns:
a new
AsyncScalarResultfiltering object referring to thisAsyncResultobject.
-
attribute
sqlalchemy.ext.asyncio.AsyncResult.t¶ Apply a “typed tuple” typing filter to returned rows.
The
AsyncResult.tattribute is a synonym for calling theAsyncResult.tuples()method.New in version 2.0.
-
method
sqlalchemy.ext.asyncio.AsyncResult.tuples() AsyncTupleResult[_TP]¶ Apply a “typed tuple” typing filter to returned rows.
This method returns the same
AsyncResultobject at runtime, however annotates as returning aAsyncTupleResultobject that will indicate to PEP 484 typing tools that plain typedTupleinstances are returned rather than rows. This allows tuple unpacking and__getitem__access ofRowobjects to by typed, for those cases where the statement invoked itself included typing information.New in version 2.0.
- Returns:
the
AsyncTupleResulttype at typing time.
-
method
sqlalchemy.ext.asyncio.AsyncResult.unique(strategy: _UniqueFilterType | None = None) Self¶ Apply unique filtering to the objects returned by this
AsyncResult.Refer to
Result.unique()in the synchronous SQLAlchemy API for a complete behavioral description.
-
method
sqlalchemy.ext.asyncio.AsyncResult.yield_per(num: int) Self¶ inherited from the
FilterResult.yield_per()method ofFilterResultConfigure the row-fetching strategy to fetch
numrows at a time.The
FilterResult.yield_per()method is a pass through to theResult.yield_per()method. See that method’s documentation for usage notes.New in version 1.4.40: - added
FilterResult.yield_per()so that the method is available on all result set implementationsSee also
Using Server Side Cursors (a.k.a. stream results) - describes Core behavior for
Result.yield_per()Fetching Large Result Sets with Yield Per - in the ORM Querying Guide
-
method
- class sqlalchemy.ext.asyncio.AsyncScalarResult¶
A wrapper for a
AsyncResultthat returns scalar values rather thanRowvalues.The
AsyncScalarResultobject is acquired by calling theAsyncResult.scalars()method.Refer to the
ScalarResultobject in the synchronous SQLAlchemy API for a complete behavioral description.New in version 1.4.
Members
all(), close(), closed, fetchall(), fetchmany(), first(), one(), one_or_none(), partitions(), unique(), yield_per()
Class signature
class
sqlalchemy.ext.asyncio.AsyncScalarResult(sqlalchemy.ext.asyncio.AsyncCommon)-
method
sqlalchemy.ext.asyncio.AsyncScalarResult.async all() Sequence[_R]¶ Return all scalar values in a list.
Equivalent to
AsyncResult.all()except that scalar values, rather thanRowobjects, are returned.
-
method
sqlalchemy.ext.asyncio.AsyncScalarResult.async close() None¶ inherited from the
AsyncCommon.close()method ofAsyncCommonClose this result.
-
attribute
sqlalchemy.ext.asyncio.AsyncScalarResult.closed¶ inherited from the
AsyncCommon.closedattribute ofAsyncCommonproxies the .closed attribute of the underlying result object, if any, else raises
AttributeError.New in version 2.0.0b3.
-
method
sqlalchemy.ext.asyncio.AsyncScalarResult.async fetchall() Sequence[_R]¶ A synonym for the
AsyncScalarResult.all()method.
-
method
sqlalchemy.ext.asyncio.AsyncScalarResult.async fetchmany(size: int | None = None) Sequence[_R]¶ Fetch many objects.
Equivalent to
AsyncResult.fetchmany()except that scalar values, rather thanRowobjects, are returned.
-
method
sqlalchemy.ext.asyncio.AsyncScalarResult.async first() _R | None¶ Fetch the first object or
Noneif no object is present.Equivalent to
AsyncResult.first()except that scalar values, rather thanRowobjects, are returned.
-
method
sqlalchemy.ext.asyncio.AsyncScalarResult.async one() _R¶ Return exactly one object or raise an exception.
Equivalent to
AsyncResult.one()except that scalar values, rather thanRowobjects, are returned.
-
method
sqlalchemy.ext.asyncio.AsyncScalarResult.async one_or_none() _R | None¶ Return at most one object or raise an exception.
Equivalent to
AsyncResult.one_or_none()except that scalar values, rather thanRowobjects, are returned.
-
method
sqlalchemy.ext.asyncio.AsyncScalarResult.async partitions(size: int | None = None) AsyncIterator[Sequence[_R]]¶ Iterate through sub-lists of elements of the size given.
Equivalent to
AsyncResult.partitions()except that scalar values, rather thanRowobjects, are returned.
-
method
sqlalchemy.ext.asyncio.AsyncScalarResult.unique(strategy: _UniqueFilterType | None = None) Self¶ Apply unique filtering to the objects returned by this
AsyncScalarResult.See
AsyncResult.unique()for usage details.
-
method
sqlalchemy.ext.asyncio.AsyncScalarResult.yield_per(num: int) Self¶ inherited from the
FilterResult.yield_per()method ofFilterResultConfigure the row-fetching strategy to fetch
numrows at a time.The
FilterResult.yield_per()method is a pass through to theResult.yield_per()method. See that method’s documentation for usage notes.New in version 1.4.40: - added
FilterResult.yield_per()so that the method is available on all result set implementationsSee also
Using Server Side Cursors (a.k.a. stream results) - describes Core behavior for
Result.yield_per()Fetching Large Result Sets with Yield Per - in the ORM Querying Guide
-
method
- class sqlalchemy.ext.asyncio.AsyncMappingResult¶
A wrapper for a
AsyncResultthat returns dictionary values rather thanRowvalues.The
AsyncMappingResultobject is acquired by calling theAsyncResult.mappings()method.Refer to the
MappingResultobject in the synchronous SQLAlchemy API for a complete behavioral description.New in version 1.4.
Members
all(), close(), closed, columns(), fetchall(), fetchmany(), fetchone(), first(), keys(), one(), one_or_none(), partitions(), unique(), yield_per()
Class signature
class
sqlalchemy.ext.asyncio.AsyncMappingResult(sqlalchemy.engine._WithKeys,sqlalchemy.ext.asyncio.AsyncCommon)-
method
sqlalchemy.ext.asyncio.AsyncMappingResult.async all() Sequence[RowMapping]¶ Return all rows in a list.
Equivalent to
AsyncResult.all()except thatRowMappingvalues, rather thanRowobjects, are returned.
-
method
sqlalchemy.ext.asyncio.AsyncMappingResult.async close() None¶ inherited from the
AsyncCommon.close()method ofAsyncCommonClose this result.
-
attribute
sqlalchemy.ext.asyncio.AsyncMappingResult.closed¶ inherited from the
AsyncCommon.closedattribute ofAsyncCommonproxies the .closed attribute of the underlying result object, if any, else raises
AttributeError.New in version 2.0.0b3.
-
method
sqlalchemy.ext.asyncio.AsyncMappingResult.columns(*col_expressions: _KeyIndexType) Self¶ Establish the columns that should be returned in each row.
-
method
sqlalchemy.ext.asyncio.AsyncMappingResult.async fetchall() Sequence[RowMapping]¶ A synonym for the
AsyncMappingResult.all()method.
-
method
sqlalchemy.ext.asyncio.AsyncMappingResult.async fetchmany(size: int | None = None) Sequence[RowMapping]¶ Fetch many rows.
Equivalent to
AsyncResult.fetchmany()except thatRowMappingvalues, rather thanRowobjects, are returned.
-
method
sqlalchemy.ext.asyncio.AsyncMappingResult.async fetchone() RowMapping | None¶ Fetch one object.
Equivalent to
AsyncResult.fetchone()except thatRowMappingvalues, rather thanRowobjects, are returned.
-
method
sqlalchemy.ext.asyncio.AsyncMappingResult.async first() RowMapping | None¶ Fetch the first object or
Noneif no object is present.Equivalent to
AsyncResult.first()except thatRowMappingvalues, rather thanRowobjects, are returned.
-
method
sqlalchemy.ext.asyncio.AsyncMappingResult.keys() RMKeyView¶ inherited from the
sqlalchemy.engine._WithKeys.keysmethod ofsqlalchemy.engine._WithKeysReturn an iterable view which yields the string keys that would be represented by each
Row.The keys can represent the labels of the columns returned by a core statement or the names of the orm classes returned by an orm execution.
The view also can be tested for key containment using the Python
inoperator, which will test both for the string keys represented in the view, as well as for alternate keys such as column objects.Changed in version 1.4: a key view object is returned rather than a plain list.
-
method
sqlalchemy.ext.asyncio.AsyncMappingResult.async one() RowMapping¶ Return exactly one object or raise an exception.
Equivalent to
AsyncResult.one()except thatRowMappingvalues, rather thanRowobjects, are returned.
-
method
sqlalchemy.ext.asyncio.AsyncMappingResult.async one_or_none() RowMapping | None¶ Return at most one object or raise an exception.
Equivalent to
AsyncResult.one_or_none()except thatRowMappingvalues, rather thanRowobjects, are returned.
-
method
sqlalchemy.ext.asyncio.AsyncMappingResult.async partitions(size: int | None = None) AsyncIterator[Sequence[RowMapping]]¶ Iterate through sub-lists of elements of the size given.
Equivalent to
AsyncResult.partitions()except thatRowMappingvalues, rather thanRowobjects, are returned.
-
method
sqlalchemy.ext.asyncio.AsyncMappingResult.unique(strategy: _UniqueFilterType | None = None) Self¶ Apply unique filtering to the objects returned by this
AsyncMappingResult.See
AsyncResult.unique()for usage details.
-
method
sqlalchemy.ext.asyncio.AsyncMappingResult.yield_per(num: int) Self¶ inherited from the
FilterResult.yield_per()method ofFilterResultConfigure the row-fetching strategy to fetch
numrows at a time.The
FilterResult.yield_per()method is a pass through to theResult.yield_per()method. See that method’s documentation for usage notes.New in version 1.4.40: - added
FilterResult.yield_per()so that the method is available on all result set implementationsSee also
Using Server Side Cursors (a.k.a. stream results) - describes Core behavior for
Result.yield_per()Fetching Large Result Sets with Yield Per - in the ORM Querying Guide
-
method
- class sqlalchemy.ext.asyncio.AsyncTupleResult¶
A
AsyncResultthat’s typed as returning plain Python tuples instead of rows.Since
Rowacts like a tuple in every way already, this class is a typing only class, regularAsyncResultis still used at runtime.Class signature
class
sqlalchemy.ext.asyncio.AsyncTupleResult(sqlalchemy.ext.asyncio.AsyncCommon,sqlalchemy.util.langhelpers.TypingOnly)
ORM Session API Documentation¶
| Object Name | Description |
|---|---|
async_object_session(instance) |
Return the |
Provides scoped management of |
|
async_session(session) |
Return the |
A configurable |
|
Mixin class which provides an awaitable accessor for all attributes. |
|
Asyncio version of |
|
A wrapper for the ORM |
|
Close all |
- function sqlalchemy.ext.asyncio.async_object_session(instance: object) AsyncSession | None¶
Return the
AsyncSessionto which the given instance belongs.This function makes use of the sync-API function
object_sessionto retrieve theSessionwhich refers to the given instance, and from there links it to the originalAsyncSession.If the
AsyncSessionhas been garbage collected, the return value isNone.This functionality is also available from the
InstanceState.async_sessionaccessor.- Parameters:
instance¶ – an ORM mapped instance
- Returns:
an
AsyncSessionobject, orNone.
New in version 1.4.18.
- function sqlalchemy.ext.asyncio.async_session(session: Session) AsyncSession | None¶
Return the
AsyncSessionwhich is proxying the givenSessionobject, if any.- Parameters:
- Returns:
a
AsyncSessioninstance, orNone.
New in version 1.4.18.
- function async sqlalchemy.ext.asyncio.close_all_sessions() None¶
Close all
AsyncSessionsessions.New in version 2.0.23.
See also
close_all_sessions()
- class sqlalchemy.ext.asyncio.async_sessionmaker¶
A configurable
AsyncSessionfactory.The
async_sessionmakerfactory works in the same way as thesessionmakerfactory, to generate newAsyncSessionobjects when called, creating them given the configurational arguments established here.e.g.:
from sqlalchemy.ext.asyncio import create_async_engine from sqlalchemy.ext.asyncio import AsyncSession from sqlalchemy.ext.asyncio import async_sessionmaker async def run_some_sql(async_session: async_sessionmaker[AsyncSession]) -> None: async with async_session() as session: session.add(SomeObject(data="object")) session.add(SomeOtherObject(name="other object")) await session.commit() async def main() -> None: # an AsyncEngine, which the AsyncSession will use for connection # resources engine = create_async_engine('postgresql+asyncpg://scott:tiger@localhost/') # create a reusable factory for new AsyncSession instances async_session = async_sessionmaker(engine) await run_some_sql(async_session) await engine.dispose()
The
async_sessionmakeris useful so that different parts of a program can create newAsyncSessionobjects with a fixed configuration established up front. Note thatAsyncSessionobjects may also be instantiated directly when not usingasync_sessionmaker.New in version 2.0:
async_sessionmakerprovides asessionmakerclass that’s dedicated to theAsyncSessionobject, including pep-484 typing support.See also
Synopsis - ORM - shows example use
sessionmaker- general overview of thesessionmakerarchitecture
Opening and Closing a Session - introductory text on creating sessions using
sessionmaker.Members
Class signature
class
sqlalchemy.ext.asyncio.async_sessionmaker(typing.Generic)-
method
sqlalchemy.ext.asyncio.async_sessionmaker.__call__(**local_kw: Any) _AS¶ Produce a new
AsyncSessionobject using the configuration established in thisasync_sessionmaker.In Python, the
__call__method is invoked on an object when it is “called” in the same way as a function:AsyncSession = async_sessionmaker(async_engine, expire_on_commit=False) session = AsyncSession() # invokes sessionmaker.__call__()
-
method
sqlalchemy.ext.asyncio.async_sessionmaker.__init__(bind: Optional[_AsyncSessionBind] = None, *, class_: Type[_AS] = <class 'sqlalchemy.ext.asyncio.session.AsyncSession'>, autoflush: bool = True, expire_on_commit: bool = True, info: Optional[_InfoType] = None, **kw: Any)¶ Construct a new
async_sessionmaker.All arguments here except for
class_correspond to arguments accepted bySessiondirectly. See theAsyncSession.__init__()docstring for more details on parameters.
-
method
sqlalchemy.ext.asyncio.async_sessionmaker.begin() _AsyncSessionContextManager[_AS]¶ Produce a context manager that both provides a new
AsyncSessionas well as a transaction that commits.e.g.:
async def main(): Session = async_sessionmaker(some_engine) async with Session.begin() as session: session.add(some_object) # commits transaction, closes session
-
method
sqlalchemy.ext.asyncio.async_sessionmaker.configure(**new_kw: Any) None¶ (Re)configure the arguments for this async_sessionmaker.
e.g.:
AsyncSession = async_sessionmaker(some_engine) AsyncSession.configure(bind=create_async_engine('sqlite+aiosqlite://'))
- class sqlalchemy.ext.asyncio.async_scoped_session¶
Provides scoped management of
AsyncSessionobjects.See the section Using asyncio scoped session for usage details.
New in version 1.4.19.
Members
__call__(), __init__(), aclose(), add(), add_all(), autoflush, begin(), begin_nested(), bind, close(), close_all(), commit(), configure(), connection(), delete(), deleted, dirty, execute(), expire(), expire_all(), expunge(), expunge_all(), flush(), get(), get_bind(), get_one(), identity_key(), identity_map, info, invalidate(), is_active, is_modified(), merge(), new, no_autoflush, object_session(), refresh(), remove(), reset(), rollback(), scalar(), scalars(), session_factory, stream(), stream_scalars()
Class signature
class
sqlalchemy.ext.asyncio.async_scoped_session(typing.Generic)-
method
sqlalchemy.ext.asyncio.async_scoped_session.__call__(**kw: Any) _AS¶ Return the current
AsyncSession, creating it using thescoped_session.session_factoryif not present.- Parameters:
**kw¶ – Keyword arguments will be passed to the
scoped_session.session_factorycallable, if an existingAsyncSessionis not present. If theAsyncSessionis present and keyword arguments have been passed,InvalidRequestErroris raised.
-
method
sqlalchemy.ext.asyncio.async_scoped_session.__init__(session_factory: async_sessionmaker[_AS], scopefunc: Callable[[], Any])¶ Construct a new
async_scoped_session.- Parameters:
session_factory¶ – a factory to create new
AsyncSessioninstances. This is usually, but not necessarily, an instance ofasync_sessionmaker.scopefunc¶ – function which defines the current scope. A function such as
asyncio.current_taskmay be useful here.
-
method
sqlalchemy.ext.asyncio.async_scoped_session.async aclose() None¶ A synonym for
AsyncSession.close().Proxied for the
AsyncSessionclass on behalf of theasync_scoped_sessionclass.The
AsyncSession.aclose()name is specifically to support the Python standard library@contextlib.aclosingcontext manager function.New in version 2.0.20.
-
method
sqlalchemy.ext.asyncio.async_scoped_session.add(instance: object, _warn: bool = True) None¶ Place an object into this
Session.Proxied for the
AsyncSessionclass on behalf of theasync_scoped_sessionclass.Proxied for the
Sessionclass on behalf of theAsyncSessionclass.Objects that are in the transient state when passed to the
Session.add()method will move to the pending state, until the next flush, at which point they will move to the persistent state.Objects that are in the detached state when passed to the
Session.add()method will move to the persistent state directly.If the transaction used by the
Sessionis rolled back, objects which were transient when they were passed toSession.add()will be moved back to the transient state, and will no longer be present within thisSession.
-
method
sqlalchemy.ext.asyncio.async_scoped_session.add_all(instances: Iterable[object]) None¶ Add the given collection of instances to this
Session.Proxied for the
AsyncSessionclass on behalf of theasync_scoped_sessionclass.Proxied for the
Sessionclass on behalf of theAsyncSessionclass.See the documentation for
Session.add()for a general behavioral description.
-
attribute
sqlalchemy.ext.asyncio.async_scoped_session.autoflush¶ Proxy for the
Session.autoflushattribute on behalf of theAsyncSessionclass.Proxied for the
AsyncSessionclass on behalf of theasync_scoped_sessionclass.
-
method
sqlalchemy.ext.asyncio.async_scoped_session.begin() AsyncSessionTransaction¶ Return an
AsyncSessionTransactionobject.Proxied for the
AsyncSessionclass on behalf of theasync_scoped_sessionclass.The underlying
Sessionwill perform the “begin” action when theAsyncSessionTransactionobject 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
SessionEvents.after_transaction_create()event hook that may perform IO.For a general description of ORM begin, see
Session.begin().
-
method
sqlalchemy.ext.asyncio.async_scoped_session.begin_nested() AsyncSessionTransaction¶ Return an
AsyncSessionTransactionobject which will begin a “nested” transaction, e.g. SAVEPOINT.Proxied for the
AsyncSessionclass on behalf of theasync_scoped_sessionclass.Behavior is the same as that of
AsyncSession.begin().For a general description of ORM begin nested, see
Session.begin_nested().See also
Serializable isolation / Savepoints / Transactional DDL (asyncio version) - special workarounds required with the SQLite asyncio driver in order for SAVEPOINT to work correctly.
-
attribute
sqlalchemy.ext.asyncio.async_scoped_session.bind¶ Proxy for the
AsyncSession.bindattribute on behalf of theasync_scoped_sessionclass.
-
method
sqlalchemy.ext.asyncio.async_scoped_session.async close() None¶ Close out the transactional resources and ORM objects used by this
AsyncSession.Proxied for the
AsyncSessionclass on behalf of theasync_scoped_sessionclass.See also
Session.close()- main documentation for “close”Closing - detail on the semantics of
AsyncSession.close()andAsyncSession.reset().
-
async classmethod
sqlalchemy.ext.asyncio.async_scoped_session.close_all() None¶ Close all
AsyncSessionsessions.Proxied for the
AsyncSessionclass on behalf of theasync_scoped_sessionclass.Deprecated since version 2.0: The
AsyncSession.close_all()method is deprecated and will be removed in a future release. Please refer toclose_all_sessions().
-
method
sqlalchemy.ext.asyncio.async_scoped_session.async commit() None¶ Commit the current transaction in progress.
Proxied for the
AsyncSessionclass on behalf of theasync_scoped_sessionclass.See also
Session.commit()- main documentation for “commit”
-
method
sqlalchemy.ext.asyncio.async_scoped_session.configure(**kwargs: Any) None¶ reconfigure the
sessionmakerused by thisscoped_session.
-
method
sqlalchemy.ext.asyncio.async_scoped_session.async connection(bind_arguments: _BindArguments | None = None, execution_options: CoreExecuteOptionsParameter | None = None, **kw: Any) AsyncConnection¶ Return a
AsyncConnectionobject corresponding to thisSessionobject’s transactional state.Proxied for the
AsyncSessionclass on behalf of theasync_scoped_sessionclass.This method may also be used to establish execution options for the database connection used by the current transaction.
New in version 1.4.24: Added **kw arguments which are passed through to the underlying
Session.connection()method.See also
Session.connection()- main documentation for “connection”
-
method
sqlalchemy.ext.asyncio.async_scoped_session.async delete(instance: object) None¶ Mark an instance as deleted.
Proxied for the
AsyncSessionclass on behalf of theasync_scoped_sessionclass.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.
See also
Session.delete()- main documentation for delete
-
attribute
sqlalchemy.ext.asyncio.async_scoped_session.deleted¶ The set of all instances marked as ‘deleted’ within this
SessionProxied for the
AsyncSessionclass on behalf of theasync_scoped_sessionclass.Proxied for the
Sessionclass on behalf of theAsyncSessionclass.
-
attribute
sqlalchemy.ext.asyncio.async_scoped_session.dirty¶ The set of all persistent instances considered dirty.
Proxied for the
AsyncSessionclass on behalf of theasync_scoped_sessionclass.Proxied for the
Sessionclass on behalf of theAsyncSessionclass.E.g.:
some_mapped_object in session.dirty
Instances are considered dirty when they were modified but not deleted.
Note that this ‘dirty’ calculation is ‘optimistic’; most attribute-setting or collection modification operations will mark an instance as ‘dirty’ and place it in this set, even if there is no net change to the attribute’s value. At flush time, the value of each attribute is compared to its previously saved value, and if there’s no net change, no SQL operation will occur (this is a more expensive operation so it’s only done at flush time).
To check if an instance has actionable net changes to its attributes, use the
Session.is_modified()method.
-
method
sqlalchemy.ext.asyncio.async_scoped_session.async execute(statement: Executable, params: _CoreAnyExecuteParams | None = None, *, execution_options: OrmExecuteOptionsParameter = {}, bind_arguments: _BindArguments | None = None, **kw: Any) Result[Any]¶ Execute a statement and return a buffered
Resultobject.Proxied for the
AsyncSessionclass on behalf of theasync_scoped_sessionclass.See also
Session.execute()- main documentation for execute
-
method
sqlalchemy.ext.asyncio.async_scoped_session.expire(instance: object, attribute_names: Iterable[str] | None = None) None¶ Expire the attributes on an instance.
Proxied for the
AsyncSessionclass on behalf of theasync_scoped_sessionclass.Proxied for the
Sessionclass on behalf of theAsyncSessionclass.Marks the attributes of an instance as out of date. When an expired attribute is next accessed, a query will be issued to the
Sessionobject’s current transactional context in order to load all expired attributes for the given instance. Note that a highly isolated transaction will return the same values as were previously read in that same transaction, regardless of changes in database state outside of that transaction.To expire all objects in the
Sessionsimultaneously, useSession.expire_all().The
Sessionobject’s default behavior is to expire all state whenever theSession.rollback()orSession.commit()methods are called, so that new state can be loaded for the new transaction. For this reason, callingSession.expire()only makes sense for the specific case that a non-ORM SQL statement was emitted in the current transaction.- Parameters:
See also
Refreshing / Expiring - introductory material
-
method
sqlalchemy.ext.asyncio.async_scoped_session.expire_all() None¶ Expires all persistent instances within this Session.
Proxied for the
AsyncSessionclass on behalf of theasync_scoped_sessionclass.Proxied for the
Sessionclass on behalf of theAsyncSessionclass.When any attributes on a persistent instance is next accessed, a query will be issued using the
Sessionobject’s current transactional context in order to load all expired attributes for the given instance. Note that a highly isolated transaction will return the same values as were previously read in that same transaction, regardless of changes in database state outside of that transaction.To expire individual objects and individual attributes on those objects, use
Session.expire().The
Sessionobject’s default behavior is to expire all state whenever theSession.rollback()orSession.commit()methods are called, so that new state can be loaded for the new transaction. For this reason, callingSession.expire_all()is not usually needed, assuming the transaction is isolated.See also
Refreshing / Expiring - introductory material
-
method
sqlalchemy.ext.asyncio.async_scoped_session.expunge(instance: object) None¶ Remove the instance from this
Session.Proxied for the
AsyncSessionclass on behalf of theasync_scoped_sessionclass.Proxied for the
Sessionclass on behalf of theAsyncSessionclass.This will free all internal references to the instance. Cascading will be applied according to the expunge cascade rule.
-
method
sqlalchemy.ext.asyncio.async_scoped_session.expunge_all() None¶ Remove all object instances from this
Session.Proxied for the
AsyncSessionclass on behalf of theasync_scoped_sessionclass.Proxied for the
Sessionclass on behalf of theAsyncSessionclass.This is equivalent to calling
expunge(obj)on all objects in thisSession.
-
method
sqlalchemy.ext.asyncio.async_scoped_session.async flush(objects: Sequence[Any] | None = None) None¶ Flush all the object changes to the database.
Proxied for the
AsyncSessionclass on behalf of theasync_scoped_sessionclass.See also
Session.flush()- main documentation for flush
-
method
sqlalchemy.ext.asyncio.async_scoped_session.async get(entity: _EntityBindKey[_O], ident: _PKIdentityArgument, *, options: Sequence[ORMOption] | None = None, populate_existing: bool = False, with_for_update: ForUpdateParameter = None, identity_token: Any | None = None, execution_options: OrmExecuteOptionsParameter = {}) _O | None¶ Return an instance based on the given primary key identifier, or
Noneif not found.Proxied for the
AsyncSessionclass on behalf of theasync_scoped_sessionclass.See also
Session.get()- main documentation for get
-
method
sqlalchemy.ext.asyncio.async_scoped_session.get_bind(mapper: _EntityBindKey[_O] | None = None, clause: ClauseElement | None = None, bind: _SessionBind | None = None, **kw: Any) Engine | Connection¶ Return a “bind” to which the synchronous proxied
Sessionis bound.Proxied for the
AsyncSessionclass on behalf of theasync_scoped_sessionclass.Unlike the
Session.get_bind()method, this method is currently not used by thisAsyncSessionin any way in order to resolve engines for requests.Note
This method proxies directly to the
Session.get_bind()method, however is currently not useful as an override target, in contrast to that of theSession.get_bind()method. The example below illustrates how to implement customSession.get_bind()schemes that work withAsyncSessionandAsyncEngine.The pattern introduced at Custom Vertical Partitioning illustrates how to apply a custom bind-lookup scheme to a
Sessiongiven a set ofEngineobjects. To apply a correspondingSession.get_bind()implementation for use with aAsyncSessionandAsyncEngineobjects, continue to subclassSessionand apply it toAsyncSessionusingAsyncSession.sync_session_class. The inner method must continue to returnEngineinstances, which can be acquired from aAsyncEngineusing theAsyncEngine.sync_engineattribute:# using example from "Custom Vertical Partitioning" import random from sqlalchemy.ext.asyncio import AsyncSession from sqlalchemy.ext.asyncio import create_async_engine from sqlalchemy.ext.asyncio import async_sessionmaker from sqlalchemy.orm import Session # 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 = async_sessionmaker( sync_session_class=RoutingSession )
The
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 viaAsyncSession.run_sync(), so routines that wish to run SQL commands inside ofSession.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.
-
method
sqlalchemy.ext.asyncio.async_scoped_session.async get_one(entity: _EntityBindKey[_O], ident: _PKIdentityArgument, *, options: Sequence[ORMOption] | None = None, populate_existing: bool = False, with_for_update: ForUpdateParameter = None, identity_token: Any | None = None, execution_options: OrmExecuteOptionsParameter = {}) _O¶ Return an instance based on the given primary key identifier, or raise an exception if not found.
Proxied for the
AsyncSessionclass on behalf of theasync_scoped_sessionclass.Raises
sqlalchemy.orm.exc.NoResultFoundif the query selects no rows...versionadded: 2.0.22
See also
Session.get_one()- main documentation for get_one
-
classmethod
sqlalchemy.ext.asyncio.async_scoped_session.identity_key(class_: Type[Any] | None = None, ident: Any | Tuple[Any, ...] = None, *, instance: Any | None = None, row: Row[Any] | RowMapping | None = None, identity_token: Any | None = None) _IdentityKeyType[Any]¶ Return an identity key.
Proxied for the
AsyncSessionclass on behalf of theasync_scoped_sessionclass.Proxied for the
Sessionclass on behalf of theAsyncSessionclass.This is an alias of
identity_key().
-
attribute
sqlalchemy.ext.asyncio.async_scoped_session.identity_map¶ Proxy for the
Session.identity_mapattribute on behalf of theAsyncSessionclass.Proxied for the
AsyncSessionclass on behalf of theasync_scoped_sessionclass.
-
attribute
sqlalchemy.ext.asyncio.async_scoped_session.info¶ A user-modifiable dictionary.
Proxied for the
AsyncSessionclass on behalf of theasync_scoped_sessionclass.Proxied for the
Sessionclass on behalf of theAsyncSessionclass.The initial value of this dictionary can be populated using the
infoargument to theSessionconstructor orsessionmakerconstructor or factory methods. The dictionary here is always local to thisSessionand can be modified independently of all otherSessionobjects.
-
method
sqlalchemy.ext.asyncio.async_scoped_session.async invalidate() None¶ Close this Session, using connection invalidation.
Proxied for the
AsyncSessionclass on behalf of theasync_scoped_sessionclass.For a complete description, see
Session.invalidate().
-
attribute
sqlalchemy.ext.asyncio.async_scoped_session.is_active¶ True if this
Sessionnot in “partial rollback” state.Proxied for the
AsyncSessionclass on behalf of theasync_scoped_sessionclass.Proxied for the
Sessionclass on behalf of theAsyncSessionclass.Changed in version 1.4: The
Sessionno longer begins a new transaction immediately, so this attribute will be False when theSessionis first instantiated.“partial rollback” state typically indicates that the flush process of the
Sessionhas failed, and that theSession.rollback()method must be emitted in order to fully roll back the transaction.If this
Sessionis not in a transaction at all, theSessionwill autobegin when it is first used, so in this caseSession.is_activewill return True.Otherwise, if this
Sessionis within a transaction, and that transaction has not been rolled back internally, theSession.is_activewill also return True.
-
method
sqlalchemy.ext.asyncio.async_scoped_session.is_modified(instance: object, include_collections: bool = True) bool¶ Return
Trueif the given instance has locally modified attributes.Proxied for the
AsyncSessionclass on behalf of theasync_scoped_sessionclass.Proxied for the
Sessionclass on behalf of theAsyncSessionclass.This method retrieves the history for each instrumented attribute on the instance and performs a comparison of the current value to its previously flushed or committed value, if any.
It is in effect a more expensive and accurate version of checking for the given instance in the
Session.dirtycollection; a full test for each attribute’s net “dirty” status is performed.E.g.:
return session.is_modified(someobject)
A few caveats to this method apply:
Instances present in the
Session.dirtycollection may reportFalsewhen tested with this method. This is because the object may have received change events via attribute mutation, thus placing it inSession.dirty, but ultimately the state is the same as that loaded from the database, resulting in no net change here.Scalar attributes may not have recorded the previously set value when a new value was applied, if the attribute was not loaded, or was expired, at the time the new value was received - in these cases, the attribute is assumed to have a change, even if there is ultimately no net change against its database value. SQLAlchemy in most cases does not need the “old” value when a set event occurs, so it skips the expense of a SQL call if the old value isn’t present, based on the assumption that an UPDATE of the scalar value is usually needed, and in those few cases where it isn’t, is less expensive on average than issuing a defensive SELECT.
The “old” value is fetched unconditionally upon set only if the attribute container has the
active_historyflag set toTrue. This flag is set typically for primary key attributes and scalar object references that are not a simple many-to-one. To set this flag for any arbitrary mapped column, use theactive_historyargument withcolumn_property().
- Parameters:
instance¶ – mapped instance to be tested for pending changes.
include_collections¶ – Indicates if multivalued collections should be included in the operation. Setting this to
Falseis a way to detect only local-column based properties (i.e. scalar columns or many-to-one foreign keys) that would result in an UPDATE for this instance upon flush.
-
method
sqlalchemy.ext.asyncio.async_scoped_session.async merge(instance: _O, *, load: bool = True, options: Sequence[ORMOption] | None = None) _O¶ Copy the state of a given instance into a corresponding instance within this
AsyncSession.Proxied for the
AsyncSessionclass on behalf of theasync_scoped_sessionclass.See also
Session.merge()- main documentation for merge
-
attribute
sqlalchemy.ext.asyncio.async_scoped_session.new¶ The set of all instances marked as ‘new’ within this
Session.Proxied for the
AsyncSessionclass on behalf of theasync_scoped_sessionclass.Proxied for the
Sessionclass on behalf of theAsyncSessionclass.
-
attribute
sqlalchemy.ext.asyncio.async_scoped_session.no_autoflush¶ Return a context manager that disables autoflush.
Proxied for the
AsyncSessionclass on behalf of theasync_scoped_sessionclass.Proxied for the
Sessionclass on behalf of theAsyncSessionclass.e.g.:
with session.no_autoflush: some_object = SomeClass() session.add(some_object) # won't autoflush some_object.related_thing = session.query(SomeRelated).first()
Operations that proceed within the
with:block will not be subject to flushes occurring upon query access. This is useful when initializing a series of objects which involve existing database queries, where the uncompleted object should not yet be flushed.
-
classmethod
sqlalchemy.ext.asyncio.async_scoped_session.object_session(instance: object) Session | None¶ Return the
Sessionto which an object belongs.Proxied for the
AsyncSessionclass on behalf of theasync_scoped_sessionclass.Proxied for the
Sessionclass on behalf of theAsyncSessionclass.This is an alias of
object_session().
-
method
sqlalchemy.ext.asyncio.async_scoped_session.async refresh(instance: object, attribute_names: Iterable[str] | None = None, with_for_update: ForUpdateParameter = None) None¶ Expire and refresh the attributes on the given instance.
Proxied for the
AsyncSessionclass on behalf of theasync_scoped_sessionclass.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
Session.refresh()method. See that method for a complete description of all options.See also
Session.refresh()- main documentation for refresh
-
method
sqlalchemy.ext.asyncio.async_scoped_session.async remove() None¶ Dispose of the current
AsyncSession, if present.Different from scoped_session’s remove method, this method would use await to wait for the close method of AsyncSession.
-
method
sqlalchemy.ext.asyncio.async_scoped_session.async reset() None¶ Close out the transactional resources and ORM objects used by this
Session, resetting the session to its initial state.Proxied for the
AsyncSessionclass on behalf of theasync_scoped_sessionclass.New in version 2.0.22.
See also
Session.reset()- main documentation for “reset”Closing - detail on the semantics of
AsyncSession.close()andAsyncSession.reset().
-
method
sqlalchemy.ext.asyncio.async_scoped_session.async rollback() None¶ Rollback the current transaction in progress.
Proxied for the
AsyncSessionclass on behalf of theasync_scoped_sessionclass.See also
Session.rollback()- main documentation for “rollback”
-
method
sqlalchemy.ext.asyncio.async_scoped_session.async scalar(statement: Executable, params: _CoreAnyExecuteParams | None = None, *, execution_options: OrmExecuteOptionsParameter = {}, bind_arguments: _BindArguments | None = None, **kw: Any) Any¶ Execute a statement and return a scalar result.
Proxied for the
AsyncSessionclass on behalf of theasync_scoped_sessionclass.See also
Session.scalar()- main documentation for scalar
-
method
sqlalchemy.ext.asyncio.async_scoped_session.async scalars(statement: Executable, params: _CoreAnyExecuteParams | None = None, *, execution_options: OrmExecuteOptionsParameter = {}, bind_arguments: _BindArguments | None = None, **kw: Any) ScalarResult[Any]¶ Execute a statement and return scalar results.
Proxied for the
AsyncSessionclass on behalf of theasync_scoped_sessionclass.- Returns:
a
ScalarResultobject
New in version 1.4.24: Added
AsyncSession.scalars()New in version 1.4.26: Added
async_scoped_session.scalars()See also
Session.scalars()- main documentation for scalarsAsyncSession.stream_scalars()- streaming version
-
attribute
sqlalchemy.ext.asyncio.async_scoped_session.session_factory: async_sessionmaker[_AS]¶ 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
AsyncSessionis needed.
-
method
sqlalchemy.ext.asyncio.async_scoped_session.async stream(statement: Executable, params: _CoreAnyExecuteParams | None = None, *, execution_options: OrmExecuteOptionsParameter = {}, bind_arguments: _BindArguments | None = None, **kw: Any) AsyncResult[Any]¶ Execute a statement and return a streaming
AsyncResultobject.Proxied for the
AsyncSessionclass on behalf of theasync_scoped_sessionclass.
-
method
sqlalchemy.ext.asyncio.async_scoped_session.async stream_scalars(statement: Executable, params: _CoreAnyExecuteParams | None = None, *, execution_options: OrmExecuteOptionsParameter = {}, bind_arguments: _BindArguments | None = None, **kw: Any) AsyncScalarResult[Any]¶ Execute a statement and return a stream of scalar results.
Proxied for the
AsyncSessionclass on behalf of theasync_scoped_sessionclass.- Returns:
an
AsyncScalarResultobject
New in version 1.4.24.
See also
Session.scalars()- main documentation for scalarsAsyncSession.scalars()- non streaming version
-
method
- class sqlalchemy.ext.asyncio.AsyncAttrs¶
Mixin class which provides an awaitable accessor for all attributes.
E.g.:
from __future__ import annotations from typing import List from sqlalchemy import ForeignKey from sqlalchemy import func from sqlalchemy.ext.asyncio import AsyncAttrs from sqlalchemy.orm import DeclarativeBase from sqlalchemy.orm import Mapped from sqlalchemy.orm import mapped_column from sqlalchemy.orm import relationship class Base(AsyncAttrs, DeclarativeBase): pass class A(Base): __tablename__ = "a" id: Mapped[int] = mapped_column(primary_key=True) data: Mapped[str] bs: Mapped[List[B]] = relationship() class B(Base): __tablename__ = "b" id: Mapped[int] = mapped_column(primary_key=True) a_id: Mapped[int] = mapped_column(ForeignKey("a.id")) data: Mapped[str]
In the above example, the
AsyncAttrsmixin is applied to the declarativeBaseclass where it takes effect for all subclasses. This mixin adds a single new attributeAsyncAttrs.awaitable_attrsto all classes, which will yield the value of any attribute as an awaitable. This allows attributes which may be subject to lazy loading or deferred / unexpiry loading to be accessed such that IO can still be emitted:a1 = (await async_session.scalars(select(A).where(A.id == 5))).one() # use the lazy loader on ``a1.bs`` via the ``.awaitable_attrs`` # interface, so that it may be awaited for b1 in await a1.awaitable_attrs.bs: print(b1)
The
AsyncAttrs.awaitable_attrsperforms a call against the attribute that is approximately equivalent to using theAsyncSession.run_sync()method, e.g.:for b1 in await async_session.run_sync(lambda sess: a1.bs): print(b1)
New in version 2.0.13.
Members
-
attribute
sqlalchemy.ext.asyncio.AsyncAttrs.awaitable_attrs¶ provide a namespace of all attributes on this object wrapped as awaitables.
e.g.:
a1 = (await async_session.scalars(select(A).where(A.id == 5))).one() some_attribute = await a1.awaitable_attrs.some_deferred_attribute some_collection = await a1.awaitable_attrs.some_collection
-
attribute
- class sqlalchemy.ext.asyncio.AsyncSession¶
Asyncio version of
Session.The
AsyncSessionis a proxy for a traditionalSessioninstance.The
AsyncSessionis not safe for use in concurrent tasks.. See Is the Session thread-safe? Is AsyncSession safe to share in concurrent tasks? for background.New in version 1.4.
To use an
AsyncSessionwith customSessionimplementations, see theAsyncSession.sync_session_classparameter.Members
sync_session_class, __init__(), aclose(), add(), add_all(), autoflush, begin(), begin_nested(), close(), close_all(), commit(), connection(), delete(), deleted, dirty, execute(), expire(), expire_all(), expunge(), expunge_all(), flush(), get(), get_bind(), get_nested_transaction(), get_one(), get_transaction(), identity_key(), identity_map, in_nested_transaction(), in_transaction(), info, invalidate(), is_active, is_modified(), merge(), new, no_autoflush, object_session(), refresh(), reset(), rollback(), run_sync(), scalar(), scalars(), stream(), stream_scalars(), sync_session
Class signature
class
sqlalchemy.ext.asyncio.AsyncSession(sqlalchemy.ext.asyncio.base.ReversibleProxy)-
attribute
sqlalchemy.ext.asyncio.AsyncSession.sync_session_class: Type[Session] = <class 'sqlalchemy.orm.session.Session'>¶ The class or callable that provides the underlying
Sessioninstance for a particularAsyncSession.At the class level, this attribute is the default value for the
AsyncSession.sync_session_classparameter. Custom subclasses ofAsyncSessioncan override this.At the instance level, this attribute indicates the current class or callable that was used to provide the
Sessioninstance for thisAsyncSessioninstance.New in version 1.4.24.
-
method
sqlalchemy.ext.asyncio.AsyncSession.__init__(bind: _AsyncSessionBind | None = None, *, binds: Dict[_SessionBindKey, _AsyncSessionBind] | None = None, sync_session_class: Type[Session] | None = None, **kw: Any)¶ Construct a new
AsyncSession.All parameters other than
sync_session_classare passed to thesync_session_classcallable directly to instantiate a newSession. Refer toSession.__init__()for parameter documentation.- Parameters:
sync_session_class¶ –
A
Sessionsubclass or other callable which will be used to construct theSessionwhich will be proxied. This parameter may be used to provide customSessionsubclasses. Defaults to theAsyncSession.sync_session_classclass-level attribute.New in version 1.4.24.
-
method
sqlalchemy.ext.asyncio.AsyncSession.async aclose() None¶ A synonym for
AsyncSession.close().The
AsyncSession.aclose()name is specifically to support the Python standard library@contextlib.aclosingcontext manager function.New in version 2.0.20.
-
method
sqlalchemy.ext.asyncio.AsyncSession.add(instance: object, _warn: bool = True) None¶ Place an object into this
Session.Proxied for the
Sessionclass on behalf of theAsyncSessionclass.Objects that are in the transient state when passed to the
Session.add()method will move to the pending state, until the next flush, at which point they will move to the persistent state.Objects that are in the detached state when passed to the
Session.add()method will move to the persistent state directly.If the transaction used by the
Sessionis rolled back, objects which were transient when they were passed toSession.add()will be moved back to the transient state, and will no longer be present within thisSession.
-
method
sqlalchemy.ext.asyncio.AsyncSession.add_all(instances: Iterable[object]) None¶ Add the given collection of instances to this
Session.Proxied for the
Sessionclass on behalf of theAsyncSessionclass.See the documentation for
Session.add()for a general behavioral description.
-
attribute
sqlalchemy.ext.asyncio.AsyncSession.autoflush¶ Proxy for the
Session.autoflushattribute on behalf of theAsyncSessionclass.
-
method
sqlalchemy.ext.asyncio.AsyncSession.begin() AsyncSessionTransaction¶ Return an
AsyncSessionTransactionobject.The underlying
Sessionwill perform the “begin” action when theAsyncSessionTransactionobject 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
SessionEvents.after_transaction_create()event hook that may perform IO.For a general description of ORM begin, see
Session.begin().
-
method
sqlalchemy.ext.asyncio.AsyncSession.begin_nested() AsyncSessionTransaction¶ Return an
AsyncSessionTransactionobject which will begin a “nested” transaction, e.g. SAVEPOINT.Behavior is the same as that of
AsyncSession.begin().For a general description of ORM begin nested, see
Session.begin_nested().See also
Serializable isolation / Savepoints / Transactional DDL (asyncio version) - special workarounds required with the SQLite asyncio driver in order for SAVEPOINT to work correctly.
-
method
sqlalchemy.ext.asyncio.AsyncSession.async close() None¶ Close out the transactional resources and ORM objects used by this
AsyncSession.See also
Session.close()- main documentation for “close”Closing - detail on the semantics of
AsyncSession.close()andAsyncSession.reset().
-
async classmethod
sqlalchemy.ext.asyncio.AsyncSession.close_all() None¶ Close all
AsyncSessionsessions.Deprecated since version 2.0: The
AsyncSession.close_all()method is deprecated and will be removed in a future release. Please refer toclose_all_sessions().
-
method
sqlalchemy.ext.asyncio.AsyncSession.async commit() None¶ Commit the current transaction in progress.
See also
Session.commit()- main documentation for “commit”
-
method
sqlalchemy.ext.asyncio.AsyncSession.async connection(bind_arguments: _BindArguments | None = None, execution_options: CoreExecuteOptionsParameter | None = None, **kw: Any) AsyncConnection¶ Return a
AsyncConnectionobject corresponding to thisSessionobject’s transactional state.This method may also be used to establish execution options for the database connection used by the current transaction.
New in version 1.4.24: Added **kw arguments which are passed through to the underlying
Session.connection()method.See also
Session.connection()- main documentation for “connection”
-
method
sqlalchemy.ext.asyncio.AsyncSession.async delete(instance: object) None¶ 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.
See also
Session.delete()- main documentation for delete
-
attribute
sqlalchemy.ext.asyncio.AsyncSession.deleted¶ The set of all instances marked as ‘deleted’ within this
SessionProxied for the
Sessionclass on behalf of theAsyncSessionclass.
-
attribute
sqlalchemy.ext.asyncio.AsyncSession.dirty¶ The set of all persistent instances considered dirty.
Proxied for the
Sessionclass on behalf of theAsyncSessionclass.E.g.:
some_mapped_object in session.dirty
Instances are considered dirty when they were modified but not deleted.
Note that this ‘dirty’ calculation is ‘optimistic’; most attribute-setting or collection modification operations will mark an instance as ‘dirty’ and place it in this set, even if there is no net change to the attribute’s value. At flush time, the value of each attribute is compared to its previously saved value, and if there’s no net change, no SQL operation will occur (this is a more expensive operation so it’s only done at flush time).
To check if an instance has actionable net changes to its attributes, use the
Session.is_modified()method.
-
method
sqlalchemy.ext.asyncio.AsyncSession.async execute(statement: Executable, params: _CoreAnyExecuteParams | None = None, *, execution_options: OrmExecuteOptionsParameter = {}, bind_arguments: _BindArguments | None = None, **kw: Any) Result[Any]¶ Execute a statement and return a buffered
Resultobject.See also
Session.execute()- main documentation for execute
-
method
sqlalchemy.ext.asyncio.AsyncSession.expire(instance: object, attribute_names: Iterable[str] | None = None) None¶ Expire the attributes on an instance.
Proxied for the
Sessionclass on behalf of theAsyncSessionclass.Marks the attributes of an instance as out of date. When an expired attribute is next accessed, a query will be issued to the
Sessionobject’s current transactional context in order to load all expired attributes for the given instance. Note that a highly isolated transaction will return the same values as were previously read in that same transaction, regardless of changes in database state outside of that transaction.To expire all objects in the
Sessionsimultaneously, useSession.expire_all().The
Sessionobject’s default behavior is to expire all state whenever theSession.rollback()orSession.commit()methods are called, so that new state can be loaded for the new transaction. For this reason, callingSession.expire()only makes sense for the specific case that a non-ORM SQL statement was emitted in the current transaction.- Parameters:
See also
Refreshing / Expiring - introductory material
-
method
sqlalchemy.ext.asyncio.AsyncSession.expire_all() None¶ Expires all persistent instances within this Session.
Proxied for the
Sessionclass on behalf of theAsyncSessionclass.When any attributes on a persistent instance is next accessed, a query will be issued using the
Sessionobject’s current transactional context in order to load all expired attributes for the given instance. Note that a highly isolated transaction will return the same values as were previously read in that same transaction, regardless of changes in database state outside of that transaction.To expire individual objects and individual attributes on those objects, use
Session.expire().The
Sessionobject’s default behavior is to expire all state whenever theSession.rollback()orSession.commit()methods are called, so that new state can be loaded for the new transaction. For this reason, callingSession.expire_all()is not usually needed, assuming the transaction is isolated.See also
Refreshing / Expiring - introductory material
-
method
sqlalchemy.ext.asyncio.AsyncSession.expunge(instance: object) None¶ Remove the instance from this
Session.Proxied for the
Sessionclass on behalf of theAsyncSessionclass.This will free all internal references to the instance. Cascading will be applied according to the expunge cascade rule.
-
method
sqlalchemy.ext.asyncio.AsyncSession.expunge_all() None¶ Remove all object instances from this
Session.Proxied for the
Sessionclass on behalf of theAsyncSessionclass.This is equivalent to calling
expunge(obj)on all objects in thisSession.
-
method
sqlalchemy.ext.asyncio.AsyncSession.async flush(objects: Sequence[Any] | None = None) None¶ Flush all the object changes to the database.
See also
Session.flush()- main documentation for flush
-
method
sqlalchemy.ext.asyncio.AsyncSession.async get(entity: _EntityBindKey[_O], ident: _PKIdentityArgument, *, options: Sequence[ORMOption] | None = None, populate_existing: bool = False, with_for_update: ForUpdateParameter = None, identity_token: Any | None = None, execution_options: OrmExecuteOptionsParameter = {}) _O | None¶ Return an instance based on the given primary key identifier, or
Noneif not found.See also
Session.get()- main documentation for get
-
method
sqlalchemy.ext.asyncio.AsyncSession.get_bind(mapper: _EntityBindKey[_O] | None = None, clause: ClauseElement | None = None, bind: _SessionBind | None = None, **kw: Any) Engine | Connection¶ Return a “bind” to which the synchronous proxied
Sessionis bound.Unlike the
Session.get_bind()method, this method is currently not used by thisAsyncSessionin any way in order to resolve engines for requests.Note
This method proxies directly to the
Session.get_bind()method, however is currently not useful as an override target, in contrast to that of theSession.get_bind()method. The example below illustrates how to implement customSession.get_bind()schemes that work withAsyncSessionandAsyncEngine.The pattern introduced at Custom Vertical Partitioning illustrates how to apply a custom bind-lookup scheme to a
Sessiongiven a set ofEngineobjects. To apply a correspondingSession.get_bind()implementation for use with aAsyncSessionandAsyncEngineobjects, continue to subclassSessionand apply it toAsyncSessionusingAsyncSession.sync_session_class. The inner method must continue to returnEngineinstances, which can be acquired from aAsyncEngineusing theAsyncEngine.sync_engineattribute:# using example from "Custom Vertical Partitioning" import random from sqlalchemy.ext.asyncio import AsyncSession from sqlalchemy.ext.asyncio import create_async_engine from sqlalchemy.ext.asyncio import async_sessionmaker from sqlalchemy.orm import Session # 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 = async_sessionmaker( sync_session_class=RoutingSession )
The
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 viaAsyncSession.run_sync(), so routines that wish to run SQL commands inside ofSession.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.
-
method
sqlalchemy.ext.asyncio.AsyncSession.get_nested_transaction() AsyncSessionTransaction | None¶ Return the current nested transaction in progress, if any.
- Returns:
an
AsyncSessionTransactionobject, orNone.
New in version 1.4.18.
-
method
sqlalchemy.ext.asyncio.AsyncSession.async get_one(entity: _EntityBindKey[_O], ident: _PKIdentityArgument, *, options: Sequence[ORMOption] | None = None, populate_existing: bool = False, with_for_update: ForUpdateParameter = None, identity_token: Any | None = None, execution_options: OrmExecuteOptionsParameter = {}) _O¶ Return an instance based on the given primary key identifier, or raise an exception if not found.
Raises
sqlalchemy.orm.exc.NoResultFoundif the query selects no rows...versionadded: 2.0.22
See also
Session.get_one()- main documentation for get_one
-
method
sqlalchemy.ext.asyncio.AsyncSession.get_transaction() AsyncSessionTransaction | None¶ Return the current root transaction in progress, if any.
- Returns:
an
AsyncSessionTransactionobject, orNone.
New in version 1.4.18.
-
classmethod
sqlalchemy.ext.asyncio.AsyncSession.identity_key(class_: Type[Any] | None = None, ident: Any | Tuple[Any, ...] = None, *, instance: Any | None = None, row: Row[Any] | RowMapping | None = None, identity_token: Any | None = None) _IdentityKeyType[Any]¶ Return an identity key.
Proxied for the
Sessionclass on behalf of theAsyncSessionclass.This is an alias of
identity_key().
-
attribute
sqlalchemy.ext.asyncio.AsyncSession.identity_map¶ Proxy for the
Session.identity_mapattribute on behalf of theAsyncSessionclass.
-
method
sqlalchemy.ext.asyncio.AsyncSession.in_nested_transaction() bool¶ Return True if this
Sessionhas begun a nested transaction, e.g. SAVEPOINT.Proxied for the
Sessionclass on behalf of theAsyncSessionclass.New in version 1.4.
-
method
sqlalchemy.ext.asyncio.AsyncSession.in_transaction() bool¶ Return True if this
Sessionhas begun a transaction.Proxied for the
Sessionclass on behalf of theAsyncSessionclass.New in version 1.4.
See also
-
attribute
sqlalchemy.ext.asyncio.AsyncSession.info¶ A user-modifiable dictionary.
Proxied for the
Sessionclass on behalf of theAsyncSessionclass.The initial value of this dictionary can be populated using the
infoargument to theSessionconstructor orsessionmakerconstructor or factory methods. The dictionary here is always local to thisSessionand can be modified independently of all otherSessionobjects.
-
method
sqlalchemy.ext.asyncio.AsyncSession.async invalidate() None¶ Close this Session, using connection invalidation.
For a complete description, see
Session.invalidate().
-
attribute
sqlalchemy.ext.asyncio.AsyncSession.is_active¶ True if this
Sessionnot in “partial rollback” state.Proxied for the
Sessionclass on behalf of theAsyncSessionclass.Changed in version 1.4: The
Sessionno longer begins a new transaction immediately, so this attribute will be False when theSessionis first instantiated.“partial rollback” state typically indicates that the flush process of the
Sessionhas failed, and that theSession.rollback()method must be emitted in order to fully roll back the transaction.If this
Sessionis not in a transaction at all, theSessionwill autobegin when it is first used, so in this caseSession.is_activewill return True.Otherwise, if this
Sessionis within a transaction, and that transaction has not been rolled back internally, theSession.is_activewill also return True.
-
method
sqlalchemy.ext.asyncio.AsyncSession.is_modified(instance: object, include_collections: bool = True) bool¶ Return
Trueif the given instance has locally modified attributes.Proxied for the
Sessionclass on behalf of theAsyncSessionclass.This method retrieves the history for each instrumented attribute on the instance and performs a comparison of the current value to its previously flushed or committed value, if any.
It is in effect a more expensive and accurate version of checking for the given instance in the
Session.dirtycollection; a full test for each attribute’s net “dirty” status is performed.E.g.:
return session.is_modified(someobject)
A few caveats to this method apply:
Instances present in the
Session.dirtycollection may reportFalsewhen tested with this method. This is because the object may have received change events via attribute mutation, thus placing it inSession.dirty, but ultimately the state is the same as that loaded from the database, resulting in no net change here.Scalar attributes may not have recorded the previously set value when a new value was applied, if the attribute was not loaded, or was expired, at the time the new value was received - in these cases, the attribute is assumed to have a change, even if there is ultimately no net change against its database value. SQLAlchemy in most cases does not need the “old” value when a set event occurs, so it skips the expense of a SQL call if the old value isn’t present, based on the assumption that an UPDATE of the scalar value is usually needed, and in those few cases where it isn’t, is less expensive on average than issuing a defensive SELECT.
The “old” value is fetched unconditionally upon set only if the attribute container has the
active_historyflag set toTrue. This flag is set typically for primary key attributes and scalar object references that are not a simple many-to-one. To set this flag for any arbitrary mapped column, use theactive_historyargument withcolumn_property().
- Parameters:
instance¶ – mapped instance to be tested for pending changes.
include_collections¶ – Indicates if multivalued collections should be included in the operation. Setting this to
Falseis a way to detect only local-column based properties (i.e. scalar columns or many-to-one foreign keys) that would result in an UPDATE for this instance upon flush.
-
method
sqlalchemy.ext.asyncio.AsyncSession.async merge(instance: _O, *, load: bool = True, options: Sequence[ORMOption] | None = None) _O¶ Copy the state of a given instance into a corresponding instance within this
AsyncSession.See also
Session.merge()- main documentation for merge
-
attribute
sqlalchemy.ext.asyncio.AsyncSession.new¶ The set of all instances marked as ‘new’ within this
Session.Proxied for the
Sessionclass on behalf of theAsyncSessionclass.
-
attribute
sqlalchemy.ext.asyncio.AsyncSession.no_autoflush¶ Return a context manager that disables autoflush.
Proxied for the
Sessionclass on behalf of theAsyncSessionclass.e.g.:
with session.no_autoflush: some_object = SomeClass() session.add(some_object) # won't autoflush some_object.related_thing = session.query(SomeRelated).first()
Operations that proceed within the
with:block will not be subject to flushes occurring upon query access. This is useful when initializing a series of objects which involve existing database queries, where the uncompleted object should not yet be flushed.
-
classmethod
sqlalchemy.ext.asyncio.AsyncSession.object_session(instance: object) Session | None¶ Return the
Sessionto which an object belongs.Proxied for the
Sessionclass on behalf of theAsyncSessionclass.This is an alias of
object_session().
-
method
sqlalchemy.ext.asyncio.AsyncSession.async refresh(instance: object, attribute_names: Iterable[str] | None = None, with_for_update: ForUpdateParameter = None) 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
Session.refresh()method. See that method for a complete description of all options.See also
Session.refresh()- main documentation for refresh
-
method
sqlalchemy.ext.asyncio.AsyncSession.async reset() None¶ Close out the transactional resources and ORM objects used by this
Session, resetting the session to its initial state.New in version 2.0.22.
See also
Session.reset()- main documentation for “reset”Closing - detail on the semantics of
AsyncSession.close()andAsyncSession.reset().
-
method
sqlalchemy.ext.asyncio.AsyncSession.async rollback() None¶ Rollback the current transaction in progress.
See also
Session.rollback()- main documentation for “rollback”
-
method
sqlalchemy.ext.asyncio.AsyncSession.async run_sync(fn: ~typing.Callable[[~typing.Concatenate[~sqlalchemy.orm.session.Session, ~_P]], ~sqlalchemy.ext.asyncio.session._T], *arg: ~typing.~_P, **kw: ~typing.~_P) _T¶ Invoke the given synchronous (i.e. not async) callable, passing a synchronous-style
Sessionas the first argument.This method allows traditional synchronous SQLAlchemy functions to run within the context of an asyncio application.
E.g.:
def some_business_method(session: Session, param: str) -> str: '''A synchronous function that does not require awaiting :param session: a SQLAlchemy Session, used synchronously :return: an optional return value is supported ''' session.add(MyObject(param=param)) session.flush() return "success" async def do_something_async(async_engine: AsyncEngine) -> None: '''an async function that uses awaiting''' with AsyncSession(async_engine) as async_session: # run some_business_method() with a sync-style # Session, proxied into an awaitable return_code = await async_session.run_sync(some_business_method, param="param1") print(return_code)
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.
Tip
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.
See also
AsyncAttrs- a mixin for ORM mapped classes that provides a similar feature more succinctly on a per-attribute basis
-
method
sqlalchemy.ext.asyncio.AsyncSession.async scalar(statement: Executable, params: _CoreAnyExecuteParams | None = None, *, execution_options: OrmExecuteOptionsParameter = {}, bind_arguments: _BindArguments | None = None, **kw: Any) Any¶ Execute a statement and return a scalar result.
See also
Session.scalar()- main documentation for scalar
-
method
sqlalchemy.ext.asyncio.AsyncSession.async scalars(statement: Executable, params: _CoreAnyExecuteParams | None = None, *, execution_options: OrmExecuteOptionsParameter = {}, bind_arguments: _BindArguments | None = None, **kw: Any) ScalarResult[Any]¶ Execute a statement and return scalar results.
- Returns:
a
ScalarResultobject
New in version 1.4.24: Added
AsyncSession.scalars()New in version 1.4.26: Added
async_scoped_session.scalars()See also
Session.scalars()- main documentation for scalarsAsyncSession.stream_scalars()- streaming version
-
method
sqlalchemy.ext.asyncio.AsyncSession.async stream(statement: Executable, params: _CoreAnyExecuteParams | None = None, *, execution_options: OrmExecuteOptionsParameter = {}, bind_arguments: _BindArguments | None = None, **kw: Any) AsyncResult[Any]¶ Execute a statement and return a streaming
AsyncResultobject.
-
method
sqlalchemy.ext.asyncio.AsyncSession.async stream_scalars(statement: Executable, params: _CoreAnyExecuteParams | None = None, *, execution_options: OrmExecuteOptionsParameter = {}, bind_arguments: _BindArguments | None = None, **kw: Any) AsyncScalarResult[Any]¶ Execute a statement and return a stream of scalar results.
- Returns:
an
AsyncScalarResultobject
New in version 1.4.24.
See also
Session.scalars()- main documentation for scalarsAsyncSession.scalars()- non streaming version
-
attribute
sqlalchemy.ext.asyncio.AsyncSession.sync_session: Session¶ Reference to the underlying
SessionthisAsyncSessionproxies requests towards.This instance can be used as an event target.
-
attribute
- class sqlalchemy.ext.asyncio.AsyncSessionTransaction¶
A wrapper for the ORM
SessionTransactionobject.This object is provided so that a transaction-holding object for the
AsyncSession.begin()may be returned.The object supports both explicit calls to
AsyncSessionTransaction.commit()andAsyncSessionTransaction.rollback(), as well as use as an async context manager.New in version 1.4.
Members
Class signature
class
sqlalchemy.ext.asyncio.AsyncSessionTransaction(sqlalchemy.ext.asyncio.base.ReversibleProxy,sqlalchemy.ext.asyncio.base.StartableContext)-
method
sqlalchemy.ext.asyncio.AsyncSessionTransaction.async commit() None¶ Commit this
AsyncTransaction.
-
method
sqlalchemy.ext.asyncio.AsyncSessionTransaction.async rollback() None¶ Roll back this
AsyncTransaction.
-
method