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.

Tip

The asyncio extension as of SQLAlchemy 1.4.3 can now be considered to be beta level software. API details are subject to change however at this point it is unlikely for there to be significant backwards-incompatible changes.

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 win32

For 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.ext.asyncio import create_async_engine


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(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())

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. The example below illustrates a complete example including mapper and session configuration:

import asyncio

from sqlalchemy import Column
from sqlalchemy import DateTime
from sqlalchemy import ForeignKey
from sqlalchemy import func
from sqlalchemy import Integer
from sqlalchemy import String
from sqlalchemy.ext.asyncio import AsyncSession
from sqlalchemy.ext.asyncio import create_async_engine
from sqlalchemy.future import select
from sqlalchemy.orm import declarative_base
from sqlalchemy.orm import relationship
from sqlalchemy.orm import selectinload
from sqlalchemy.orm import sessionmaker

Base = declarative_base()


class A(Base):
    __tablename__ = "a"

    id = Column(Integer, primary_key=True)
    data = Column(String)
    create_date = Column(DateTime, server_default=func.now())
    bs = relationship("B")

    # required in order to access columns with server defaults
    # or SQL expression defaults, subsequent to a flush, without
    # triggering an expired load
    __mapper_args__ = {"eager_defaults": True}


class B(Base):
    __tablename__ = "b"
    id = Column(Integer, primary_key=True)
    a_id = Column(ForeignKey("a.id"))
    data = Column(String)


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)

    # expire_on_commit=False will prevent attributes from being expired
    # after commit.
    async_session = sessionmaker(engine, expire_on_commit=False, class_=AsyncSession)

    async with async_session() 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"),
                ]
            )

        stmt = select(A).options(selectinload(A.bs))

        result = await session.execute(stmt)

        for a1 in result.scalars():
            print(a1)
            print(f"created at: {a1.create_date}")
            for b1 in a1.bs:
                print(b1)

        result = await session.execute(select(A).order_by(A.id))

        a1 = result.scalars().first()

        a1.data = "new data"

        await session.commit()

        # access attribute subsequent to commit; this is what
        # expire_on_commit=False allows
        print(a1.data)

    # for AsyncEngine created in function scope, close and
    # clean-up pooled connections
    await engine.dispose()


asyncio.run(async_main())

In the example above, the AsyncSession is instantiated using the optional sessionmaker helper, and associated with an AsyncEngine against particular database URL. It is then 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.

Note

AsyncSession uses SQLAlchemy’s future mode, which has several potentially breaking changes. One such change is the new default behavior of cascade_backrefs is False, which may affect how related objects are saved to the database.

See also

cascade_backrefs behavior deprecated for removal in 2.0

Preventing Implicit IO when Using AsyncSession

Using traditional asyncio, the application needs to avoid any points at which IO-on-attribute access may occur. Above, the following measures are taken to prevent this:

• The selectinload() eager loader is employed in order to eagerly load the A.bs collection within the scope of the await session.execute() call:

  stmt = select(A).options(selectinload(A.bs))

  If the default loader strategy of “lazyload” were left in place, the access of the A.bs attribute would raise an asyncio exception. There are a variety of ORM loader options available, which may be configured at the default mapping level or used on a per-query basis, documented at Relationship Loading Techniques.

• The AsyncSession is configured using Session.expire_on_commit set to False, so that we may access attributes on an object subsequent to a call to AsyncSession.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 = sessionmaker(
      engine, expire_on_commit=False, class_=AsyncSession
  )
  
  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)

• The Column.server_default value on the created_at column will not be refreshed by default after an INSERT; instead, it is normally expired so that it can be loaded when needed. Similar behavior applies to a column where the Column.default parameter is assigned to a SQL expression object. To access this value with asyncio, it has to be refreshed within the flush process, which is achieved by setting the mapper.eager_defaults parameter on the mapping:

  class A(Base):
      # ...
  
      # column with a server_default, or SQL expression default
      create_date = Column(DateTime, server_default=func.now())
  
      # add this so that it can be accessed
      __mapper_args__ = {"eager_defaults": True}

Other guidelines include:

• Methods like AsyncSession.expire() should be avoided in favor of AsyncSession.refresh()

• Avoid using the all cascade option documented at Cascades in favor of listing out the desired cascade features explicitly. The all cascade option implies among others the refresh-expire setting, which means that the AsyncSession.refresh() method will expire the attributes on related objects, but not necessarily refresh those related objects assuming eager loading is not configured within the relationship(), leaving them in an expired state. A future release may introduce the ability to indicate eager loader options when invoking Session.refresh() and/or AsyncSession.refresh().

• Appropriate loader options should be employed for deferred() columns, if used at all, in addition to that of relationship() constructs as noted above. See Deferred Column Loading 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 .statement attribute 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()

  See also

  Making use of “dynamic” relationship loads without using Query - notes on migration to 2.0 style

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:

1. 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 the gevent event loop.

2. 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.Queue for pooling connections.

3. 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.

4. The underlying network drivers are also using pure Python asyncio concepts, no third party networking libraries as gevent and eventlet provides 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 AsyncEngine instance) by associating the event with the sync attribute that refers to the proxied object. For example to register the PoolEvents.connect() event against an AsyncEngine instance, use its AsyncEngine.sync_engine attribute as target. Targets include:

  AsyncEngine.sync_engine

  AsyncConnection.sync_connection

  AsyncConnection.sync_engine

  AsyncSession.sync_session

• To register an event at the class level, targeting all instances of the same type (e.g. all AsyncSession instances), use the corresponding sync-style class. For example to register the SessionEvents.before_commit() event against the AsyncSession class, use the Session class as the target.

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.

Some examples of sync style event handlers associated with async-facing API constructs are illustrated below:

import asyncio

from sqlalchemy import event, text
from sqlalchemy.engine import Engine
from sqlalchemy.ext.asyncio import AsyncSession, create_async_engine
from sqlalchemy.orm import Session

## Core events ##

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!")


## ORM events ##

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())

The above example prints something along the lines of:

New DBAPI connection: <AdaptedConnection <asyncpg.connection.Connection ...>>
execute from event
before execute!
before commit!
execute from event
after commit!

asyncio and events, two opposites

SQLAlchemy events by their nature take place within the interior of a particular SQLAlchemy process; that is, an event always occurs after some particular SQLAlchemy API has been invoked by end-user code, and before some other internal aspect of that API occurs.

Constrast this to the architecture of the asyncio extension, which takes place on the exterior of SQLAlchemy’s usual flow from end-user API to DBAPI function.

The flow of messaging may be visualized as follows:

 SQLAlchemy    SQLAlchemy        SQLAlchemy          SQLAlchemy   plain
  asyncio      asyncio           ORM/Core            asyncio      asyncio
  (public      (internal)                            (internal)
  facing)
-------------|------------|------------------------|-----------|------------
asyncio API  |            |                        |           |
call  ->     |            |                        |           |
             |  ->  ->    |                        |  ->  ->   |
             |~~~~~~~~~~~~| sync API call ->       |~~~~~~~~~~~|
             | asyncio    |  event hooks ->        | sync      |
             | to         |   invoke action ->     | to        |
             | sync       |    event hooks ->      | asyncio   |
             | (greenlet) |     dialect ->         | (leave    |
             |~~~~~~~~~~~~|      event hooks ->    | greenlet) |
             |  ->  ->    |       sync adapted     |~~~~~~~~~~~|
             |            |               DBAPI -> |  ->  ->   | asyncio
             |            |                        |           | driver -> database

Where above, an API call always starts as asyncio, flows through the synchronous API, and ends as asyncio, before results are propagated through this same chain in the opposite direction. In between, the message is adapted first into sync-style API use, and then back out to async style. Event hooks then by their nature occur in the middle of the “sync-style API use”. From this it follows that the API presented within event hooks occurs inside the process by which asyncio API requests have been adapted to sync, and outgoing messages to the database API will be converted to asyncio transparently.

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, ...):
    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.orm import sessionmaker
from sqlalchemy.ext.asyncio import async_scoped_session
from sqlalchemy.ext.asyncio import AsyncSession

async_session_factory = sessionmaker(some_async_engine, class_=AsyncSession)
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())

See also

Reflecting Database Objects

Runtime Inspection API

Engine API Documentation

Object Name	Description
async_engine_from_config(configuration[, prefix], **kwargs)	Create a new AsyncEngine instance using a configuration dictionary.
AsyncConnection	An asyncio proxy for a Connection.
AsyncEngine	An asyncio proxy for a Engine.
AsyncTransaction	An asyncio proxy for a Transaction.
create_async_engine(*arg, **kw)	Create a new async engine instance.

function sqlalchemy.ext.asyncio.create_async_engine(*arg, **kw)

Create a new async engine instance.

Arguments passed to create_async_engine() are mostly identical to those passed to the create_engine() function. The specified dialect must be an asyncio-compatible dialect such as asyncpg.

New in version 1.4.

function sqlalchemy.ext.asyncio.async_engine_from_config(configuration, prefix='sqlalchemy.', **kwargs)

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 of engine_from_config().

New in version 1.4.29.

class sqlalchemy.ext.asyncio.AsyncEngine(sync_engine)

An asyncio proxy for a Engine.

AsyncEngine is acquired using the create_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(), dispose(), execution_options(), get_execution_options(), raw_connection(), sync_engine, update_execution_options()

Class signature

class sqlalchemy.ext.asyncio.AsyncEngine (sqlalchemy.ext.asyncio.base.ProxyComparable, sqlalchemy.ext.asyncio.AsyncConnectable)

method sqlalchemy.ext.asyncio.AsyncEngine.begin()

Return a context manager which when entered will deliver an AsyncConnection with an AsyncTransaction established.

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()

Clear the compiled cache associated with the dialect.

Proxied for the Engine class on behalf of the AsyncEngine class.

This applies only to the built-in cache that is established via the create_engine.query_cache_size parameter. It will not impact any dictionary caches that were passed via the Connection.execution_options.query_cache parameter.

New in version 1.4.

method sqlalchemy.ext.asyncio.AsyncEngine.connect()

Return an AsyncConnection object.

The AsyncConnection will 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 AsyncConnection may also be started outside of a context manager by invoking its AsyncConnection.start() method.

method sqlalchemy.ext.asyncio.AsyncEngine.async dispose()

Dispose of the connection pool used by this AsyncEngine.

This will close all connection pool connections that are currently checked in. See the documentation for the underlying Engine.dispose() method for further notes.

See also

Engine.dispose()

method sqlalchemy.ext.asyncio.AsyncEngine.execution_options(**opt)

Return a new AsyncEngine that will provide AsyncConnection objects with the given execution options.

Proxied from Engine.execution_options(). See that method for details.

method sqlalchemy.ext.asyncio.AsyncEngine.get_execution_options()

Get the non-SQL options which will take effect during execution.

Proxied for the Engine class on behalf of the AsyncEngine class.

See also

Engine.execution_options()

method sqlalchemy.ext.asyncio.AsyncEngine.async raw_connection()

Return a “raw” DBAPI connection from the connection pool.

See also

Working with Driver SQL and Raw DBAPI Connections

attribute sqlalchemy.ext.asyncio.AsyncEngine.sync_engine: Engine

Reference to the sync-style Engine this AsyncEngine proxies requests towards.

This instance can be used as an event target.

See also

Using events with the asyncio extension

method sqlalchemy.ext.asyncio.AsyncEngine.update_execution_options(**opt)

Update the default execution_options dictionary of this Engine.

Proxied for the Engine class on behalf of the AsyncEngine class.

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_options parameter to create_engine().

See also

Connection.execution_options()

Engine.execution_options()

class sqlalchemy.ext.asyncio.AsyncConnection(async_engine, sync_connection=None)

An asyncio proxy for a Connection.

AsyncConnection is acquired using the AsyncEngine.connect() method of AsyncEngine:

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

begin(), begin_nested(), close(), commit(), connection, exec_driver_sql(), execute(), execution_options(), get_nested_transaction(), get_raw_connection(), get_transaction(), in_nested_transaction(), in_transaction(), info, invalidate(), 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.begin()

Begin a transaction prior to autobegin occurring.

method sqlalchemy.ext.asyncio.AsyncConnection.begin_nested()

Begin a nested transaction and return a transaction handle.

method sqlalchemy.ext.asyncio.AsyncConnection.async close()

Close this AsyncConnection.

This has the effect of also rolling back the transaction if one is in place.

method sqlalchemy.ext.asyncio.AsyncConnection.async commit()

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 Connection automatically whenever a statement is first executed, or when the Connection.begin() method is called.

attribute sqlalchemy.ext.asyncio.AsyncConnection.connection

Not implemented for async; call AsyncConnection.get_raw_connection().

method sqlalchemy.ext.asyncio.AsyncConnection.async exec_driver_sql(statement, parameters=None, execution_options={})

Executes a driver-level SQL string and return buffered Result.

method sqlalchemy.ext.asyncio.AsyncConnection.async execute(statement, parameters=None, execution_options={})

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 ClauseElement and Executable hierarchies, including:

  • Select

  • Insert, Update, Delete

  • TextClause and TextualSelect

  • DDL and objects which inherit from DDLElement

• 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 DBAPI cursor.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 Result object.

method sqlalchemy.ext.asyncio.AsyncConnection.async execution_options(**opt)

Set non-SQL options for the connection which take effect during execution.

This returns this AsyncConnection object with the new options added.

See Connection.execution_options() for full details on this method.

method sqlalchemy.ext.asyncio.AsyncConnection.get_nested_transaction()

Return an AsyncTransaction representing the current nested (savepoint) transaction, if any.

This makes use of the underlying synchronous connection’s Connection.get_nested_transaction() method to get the current Transaction, which is then proxied in a new AsyncTransaction object.

New in version 1.4.0b2.

method sqlalchemy.ext.asyncio.AsyncConnection.async get_raw_connection()

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_connection that refers to the actual driver connection. Its _ConnectionFairy.dbapi_connection refers instead to an AdaptedConnection instance that adapts the driver connection to the DBAPI protocol.

method sqlalchemy.ext.asyncio.AsyncConnection.get_transaction()

Return an AsyncTransaction representing the current transaction, if any.

This makes use of the underlying synchronous connection’s Connection.get_transaction() method to get the current Transaction, which is then proxied in a new AsyncTransaction object.

New in version 1.4.0b2.

method sqlalchemy.ext.asyncio.AsyncConnection.in_nested_transaction()

Return True if a transaction is in progress.

New in version 1.4.0b2.

method sqlalchemy.ext.asyncio.AsyncConnection.in_transaction()

Return True if a transaction is in progress.

New in version 1.4.0b2.

attribute sqlalchemy.ext.asyncio.AsyncConnection.info

Return the Connection.info dictionary of the underlying Connection.

This dictionary is freely writable for user-defined state to be associated with the database connection.

This attribute is only available if the AsyncConnection is currently connected. If the AsyncConnection.closed attribute is True, then accessing this attribute will raise ResourceClosedError.

New in version 1.4.0b2.

method sqlalchemy.ext.asyncio.AsyncConnection.async invalidate(exception=None)

Invalidate the underlying DBAPI connection associated with this Connection.

See the method Connection.invalidate() for full detail on this method.

method sqlalchemy.ext.asyncio.AsyncConnection.async rollback()

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 Connection automatically whenever a statement is first executed, or when the Connection.begin() method is called.

method sqlalchemy.ext.asyncio.AsyncConnection.async run_sync(fn, *arg, **kw)

Invoke the given sync callable passing self as the first argument.

This method maintains the asyncio event loop all the way through to the database connection by running the given callable in a specially instrumented greenlet.

E.g.:

with 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.

See also

Running Synchronous Methods and Functions under asyncio

method sqlalchemy.ext.asyncio.AsyncConnection.async scalar(statement, parameters=None, execution_options={})

Executes a SQL statement construct and returns a scalar object.

This method is shorthand for invoking the Result.scalar() method after invoking the Connection.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, parameters=None, execution_options={})

Executes a SQL statement construct and returns a scalar objects.

This method is shorthand for invoking the Result.scalars() method after invoking the Connection.execute() method. Parameters are equivalent.

Returns:

a ScalarResult object.

New in version 1.4.24.

method sqlalchemy.ext.asyncio.AsyncConnection.async start(is_ctxmanager=False)

Start this AsyncConnection object’s context outside of using a Python with: block.

method sqlalchemy.ext.asyncio.AsyncConnection.async stream(statement, parameters=None, execution_options={})

Execute a statement and return a streaming AsyncResult object.

method sqlalchemy.ext.asyncio.AsyncConnection.async stream_scalars(statement, parameters=None, execution_options={})

Executes a SQL statement and returns a streaming scalar result object.

This method is shorthand for invoking the AsyncResult.scalars() method after invoking the Connection.stream() method. Parameters are equivalent.

Returns:

an AsyncScalarResult object.

New in version 1.4.24.

attribute sqlalchemy.ext.asyncio.AsyncConnection.sync_connection: Connection

Reference to the sync-style Connection this AsyncConnection proxies requests towards.

This instance can be used as an event target.

See also

Using events with the asyncio extension

attribute sqlalchemy.ext.asyncio.AsyncConnection.sync_engine: Engine

Reference to the sync-style Engine this AsyncConnection is associated with via its underlying Connection.

This instance can be used as an event target.

See also

Using events with the asyncio extension

class sqlalchemy.ext.asyncio.AsyncTransaction(connection, nested=False)

An asyncio proxy for a Transaction.

Members

close(), commit(), rollback(), start()

Class signature

class sqlalchemy.ext.asyncio.AsyncTransaction (sqlalchemy.ext.asyncio.base.ProxyComparable, sqlalchemy.ext.asyncio.base.StartableContext)

method sqlalchemy.ext.asyncio.AsyncTransaction.async close()

Close this Transaction.

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()

Commit this Transaction.

method sqlalchemy.ext.asyncio.AsyncTransaction.async rollback()

Roll back this Transaction.

method sqlalchemy.ext.asyncio.AsyncTransaction.async start(is_ctxmanager=False)

Start this AsyncTransaction object’s context outside of using a Python with: block.

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
AsyncMappingResult	A wrapper for a AsyncResult that returns dictionary values rather than Row values.
AsyncResult	An asyncio wrapper around a Result object.
AsyncScalarResult	A wrapper for a AsyncResult that returns scalar values rather than Row values.

class sqlalchemy.ext.asyncio.AsyncResult(real_result)

An asyncio wrapper around a Result object.

The AsyncResult only applies to statement executions that use a server-side cursor. It is returned only from the AsyncConnection.stream() and AsyncSession.stream() methods.

Note

As is the case with Result, this object is used for ORM results returned by AsyncSession.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 legacy Query object. For in-Python de-duplication of instances or rows, use the AsyncResult.unique() modifier method.

New in version 1.4.

Members

all(), close(), closed, columns(), fetchmany(), fetchone(), first(), freeze(), keys(), mappings(), memoized_instancemethod(), one(), one_or_none(), partitions(), scalar(), scalar_one(), scalar_one_or_none(), scalars(), unique(), yield_per()

Class signature

class sqlalchemy.ext.asyncio.AsyncResult (sqlalchemy.engine._WithKeys, sqlalchemy.ext.asyncio.AsyncCommon)

method sqlalchemy.ext.asyncio.AsyncResult.async all()

Return all rows in a list.

Closes the result set after invocation. Subsequent invocations will return an empty list.

Returns:

a list of Row objects.

method sqlalchemy.ext.asyncio.AsyncResult.async close()

inherited from the AsyncCommon.close() method of AsyncCommon

Close this result.

attribute sqlalchemy.ext.asyncio.AsyncResult.closed

inherited from the FilterResult.closed attribute of FilterResult

Return True if the underlying Result reports closed

New in version 1.4.43.

method sqlalchemy.ext.asyncio.AsyncResult.columns(*col_expressions)

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 fetchmany(size=None)

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 Row objects.

See also

AsyncResult.partitions()

method sqlalchemy.ext.asyncio.AsyncResult.async fetchone()

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 the AsyncResult object directly.

Returns:

a Row object if no filters are applied, or None if no rows remain.

method sqlalchemy.ext.asyncio.AsyncResult.async first()

Fetch the first row or None if 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 combine AsyncResult.scalars() and AsyncResult.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 this AsyncResult; 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

ORM Query Unified with Core Select

Returns:

a Row object, or None if no rows remain.

See also

AsyncResult.scalar()

AsyncResult.one()

method sqlalchemy.ext.asyncio.AsyncResult.async freeze()

Return a callable object that will produce copies of this AsyncResult when 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 FrozenResult is retrieved from a cache, it can be called any number of times where it will produce a new Result object 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()

inherited from the sqlalchemy.engine._WithKeys.keys method of sqlalchemy.engine._WithKeys

Return 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 in operator, 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()

Apply a mappings filter to returned rows, returning an instance of AsyncMappingResult.

When this filter is applied, fetching rows will return RowMapping objects instead of Row objects.

Returns:

a new AsyncMappingResult filtering object referring to the underlying Result object.

classmethod sqlalchemy.ext.asyncio.AsyncResult.memoized_instancemethod(fn)

inherited from the HasMemoized.memoized_instancemethod() method of HasMemoized

Decorate a method memoize its return value.

method sqlalchemy.ext.asyncio.AsyncResult.async one()

Return exactly one row or raise an exception.

Raises NoResultFound if the result returns no rows, or MultipleResultsFound if 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 combine AsyncResult.scalars() and AsyncResult.one().

New in version 1.4.

Returns:

The first Row.

Raises:

MultipleResultsFound, NoResultFound

See also

AsyncResult.first()

AsyncResult.one_or_none()

AsyncResult.scalar_one()

method sqlalchemy.ext.asyncio.AsyncResult.async one_or_none()

Return at most one result or raise an exception.

Returns None if the result has no rows. Raises MultipleResultsFound if multiple rows are returned.

New in version 1.4.

Returns:

The first Row or None if no row is available.

Raises:

MultipleResultsFound

See also

AsyncResult.first()

AsyncResult.one()

method sqlalchemy.ext.asyncio.AsyncResult.async partitions(size=None)

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()

Fetch the first column of the first row, and close the result set.

Returns None if 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 None if no rows remain.

method sqlalchemy.ext.asyncio.AsyncResult.async scalar_one()

Return exactly one scalar result or raise an exception.

This is equivalent to calling AsyncResult.scalars() and then AsyncResult.one().

See also

AsyncResult.one()

AsyncResult.scalars()

method sqlalchemy.ext.asyncio.AsyncResult.async scalar_one_or_none()

Return exactly one scalar result or None.

This is equivalent to calling AsyncResult.scalars() and then AsyncResult.one_or_none().

See also

AsyncResult.one_or_none()

AsyncResult.scalars()

method sqlalchemy.ext.asyncio.AsyncResult.scalars(index=0)

Return an AsyncScalarResult filtering object which will return single elements rather than Row objects.

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 0 indicating the first column.

Returns:

a new AsyncScalarResult filtering object referring to this AsyncResult object.

method sqlalchemy.ext.asyncio.AsyncResult.unique(strategy=None)

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)

inherited from the FilterResult.yield_per() method of FilterResult

Configure the row-fetching strategy to fetch num rows at a time.

The FilterResult.yield_per() method is a pass through to the Result.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 implementations

See 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

class sqlalchemy.ext.asyncio.AsyncScalarResult(real_result, index)

A wrapper for a AsyncResult that returns scalar values rather than Row values.

The AsyncScalarResult object is acquired by calling the AsyncResult.scalars() method.

Refer to the ScalarResult object in the synchronous SQLAlchemy API for a complete behavioral description.

New in version 1.4.

Members

all(), close(), closed, fetchall(), fetchmany(), first(), memoized_instancemethod(), 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()

Return all scalar values in a list.

Equivalent to AsyncResult.all() except that scalar values, rather than Row objects, are returned.

method sqlalchemy.ext.asyncio.AsyncScalarResult.async close()

inherited from the AsyncCommon.close() method of AsyncCommon

Close this result.

attribute sqlalchemy.ext.asyncio.AsyncScalarResult.closed

inherited from the FilterResult.closed attribute of FilterResult

Return True if the underlying Result reports closed

New in version 1.4.43.

method sqlalchemy.ext.asyncio.AsyncScalarResult.async fetchall()

A synonym for the AsyncScalarResult.all() method.

method sqlalchemy.ext.asyncio.AsyncScalarResult.async fetchmany(size=None)

Fetch many objects.

Equivalent to AsyncResult.fetchmany() except that scalar values, rather than Row objects, are returned.

method sqlalchemy.ext.asyncio.AsyncScalarResult.async first()

Fetch the first object or None if no object is present.

Equivalent to AsyncResult.first() except that scalar values, rather than Row objects, are returned.

classmethod sqlalchemy.ext.asyncio.AsyncScalarResult.memoized_instancemethod(fn)

inherited from the HasMemoized.memoized_instancemethod() method of HasMemoized

Decorate a method memoize its return value.

method sqlalchemy.ext.asyncio.AsyncScalarResult.async one()

Return exactly one object or raise an exception.

Equivalent to AsyncResult.one() except that scalar values, rather than Row objects, are returned.

method sqlalchemy.ext.asyncio.AsyncScalarResult.async one_or_none()

Return at most one object or raise an exception.

Equivalent to AsyncResult.one_or_none() except that scalar values, rather than Row objects, are returned.

method sqlalchemy.ext.asyncio.AsyncScalarResult.async partitions(size=None)

Iterate through sub-lists of elements of the size given.

Equivalent to AsyncResult.partitions() except that scalar values, rather than Row objects, are returned.

method sqlalchemy.ext.asyncio.AsyncScalarResult.unique(strategy=None)

Apply unique filtering to the objects returned by this AsyncScalarResult.

See AsyncResult.unique() for usage details.

method sqlalchemy.ext.asyncio.AsyncScalarResult.yield_per(num)

inherited from the FilterResult.yield_per() method of FilterResult

Configure the row-fetching strategy to fetch num rows at a time.

The FilterResult.yield_per() method is a pass through to the Result.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 implementations

See 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

class sqlalchemy.ext.asyncio.AsyncMappingResult(result)

A wrapper for a AsyncResult that returns dictionary values rather than Row values.

The AsyncMappingResult object is acquired by calling the AsyncResult.mappings() method.

Refer to the MappingResult object 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(), memoized_instancemethod(), 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()

Return all scalar values in a list.

Equivalent to AsyncResult.all() except that RowMapping values, rather than Row objects, are returned.

method sqlalchemy.ext.asyncio.AsyncMappingResult.async close()

inherited from the AsyncCommon.close() method of AsyncCommon

Close this result.

attribute sqlalchemy.ext.asyncio.AsyncMappingResult.closed

inherited from the FilterResult.closed attribute of FilterResult

Return True if the underlying Result reports closed

New in version 1.4.43.

method sqlalchemy.ext.asyncio.AsyncMappingResult.columns(*col_expressions)

Establish the columns that should be returned in each row.

method sqlalchemy.ext.asyncio.AsyncMappingResult.async fetchall()

A synonym for the AsyncMappingResult.all() method.

method sqlalchemy.ext.asyncio.AsyncMappingResult.async fetchmany(size=None)

Fetch many objects.

Equivalent to AsyncResult.fetchmany() except that RowMapping values, rather than Row objects, are returned.

method sqlalchemy.ext.asyncio.AsyncMappingResult.async fetchone()

Fetch one object.

Equivalent to AsyncResult.fetchone() except that RowMapping values, rather than Row objects, are returned.

method sqlalchemy.ext.asyncio.AsyncMappingResult.async first()

Fetch the first object or None if no object is present.

Equivalent to AsyncResult.first() except that RowMapping values, rather than Row objects, are returned.

method sqlalchemy.ext.asyncio.AsyncMappingResult.keys()

inherited from the sqlalchemy.engine._WithKeys.keys method of sqlalchemy.engine._WithKeys

Return 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 in operator, 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.

classmethod sqlalchemy.ext.asyncio.AsyncMappingResult.memoized_instancemethod(fn)

inherited from the HasMemoized.memoized_instancemethod() method of HasMemoized

Decorate a method memoize its return value.

method sqlalchemy.ext.asyncio.AsyncMappingResult.async one()

Return exactly one object or raise an exception.

Equivalent to AsyncResult.one() except that RowMapping values, rather than Row objects, are returned.

method sqlalchemy.ext.asyncio.AsyncMappingResult.async one_or_none()

Return at most one object or raise an exception.

Equivalent to AsyncResult.one_or_none() except that RowMapping values, rather than Row objects, are returned.

method sqlalchemy.ext.asyncio.AsyncMappingResult.async partitions(size=None)

Iterate through sub-lists of elements of the size given.

Equivalent to AsyncResult.partitions() except that RowMapping values, rather than Row objects, are returned.

method sqlalchemy.ext.asyncio.AsyncMappingResult.unique(strategy=None)

Apply unique filtering to the objects returned by this AsyncMappingResult.

See AsyncResult.unique() for usage details.

method sqlalchemy.ext.asyncio.AsyncMappingResult.yield_per(num)

inherited from the FilterResult.yield_per() method of FilterResult

Configure the row-fetching strategy to fetch num rows at a time.

The FilterResult.yield_per() method is a pass through to the Result.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 implementations

See 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

ORM Session API Documentation

Object Name	Description
async_object_session(instance)	Return the AsyncSession to which the given instance belongs.
async_scoped_session	Provides scoped management of AsyncSession objects.
async_session(session)	Return the AsyncSession which is proxying the given Session object, if any.
AsyncSession	Asyncio version of Session.
AsyncSessionTransaction	A wrapper for the ORM SessionTransaction object.

function sqlalchemy.ext.asyncio.async_object_session(instance)

Return the AsyncSession to which the given instance belongs.

This function makes use of the sync-API function object_session to retrieve the Session which refers to the given instance, and from there links it to the original AsyncSession.

If the AsyncSession has been garbage collected, the return value is None.

This functionality is also available from the InstanceState.async_session accessor.

Parameters:

instance – an ORM mapped instance

Returns:

an AsyncSession object, or None.

New in version 1.4.18.

function sqlalchemy.ext.asyncio.async_session(session)

Return the AsyncSession which is proxying the given Session object, if any.

Parameters:

session – a Session instance.

Returns:

a AsyncSession instance, or None.

New in version 1.4.18.

class sqlalchemy.ext.asyncio.async_scoped_session(session_factory, scopefunc)

Provides scoped management of AsyncSession objects.

See the section Using asyncio scoped session for usage details.

New in version 1.4.19.

Members

__call__(), __init__(), add(), add_all(), autoflush, begin(), begin_nested(), close(), close_all(), commit(), configure(), connection(), delete(), deleted, dirty, execute(), expire(), expire_all(), expunge(), expunge_all(), flush(), get(), get_bind(), identity_key(), identity_map, info, invalidate(), is_active, is_modified(), merge(), new, no_autoflush, object_session(), refresh(), remove(), rollback(), scalar(), scalars(), stream(), stream_scalars()

Class signature

class sqlalchemy.ext.asyncio.async_scoped_session (sqlalchemy.orm.scoping.ScopedSessionMixin)

method sqlalchemy.ext.asyncio.async_scoped_session.__call__(**kw)

inherited from the sqlalchemy.orm.scoping.ScopedSessionMixin.__call__ method of ScopedSessionMixin

Return the current Session, creating it using the scoped_session.session_factory if not present.

Parameters:

**kw – Keyword arguments will be passed to the scoped_session.session_factory callable, if an existing Session is not present. If the Session is present and keyword arguments have been passed, InvalidRequestError is raised.

method sqlalchemy.ext.asyncio.async_scoped_session.__init__(session_factory, scopefunc)

Construct a new async_scoped_session.

Parameters:

• session_factory –

  a factory to create new AsyncSession instances. This is usually, but not necessarily, an instance of sessionmaker which itself was passed the AsyncSession to its sessionmaker.class_ parameter:

  async_session_factory = sessionmaker(some_async_engine, class_= AsyncSession)
  AsyncSession = async_scoped_session(async_session_factory, scopefunc=current_task)

• scopefunc – function which defines the current scope. A function such as asyncio.current_task may be useful here.

method sqlalchemy.ext.asyncio.async_scoped_session.add(instance, _warn=True)

Place an object into this Session.

Proxied for the AsyncSession class on behalf of the async_scoped_session class.

Proxied for the Session class on behalf of the AsyncSession class.

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 Session is rolled back, objects which were transient when they were passed to Session.add() will be moved back to the transient state, and will no longer be present within this Session.

See also

Session.add_all()

Adding New or Existing Items - at Basics of Using a Session

method sqlalchemy.ext.asyncio.async_scoped_session.add_all(instances)

Add the given collection of instances to this Session.

Proxied for the AsyncSession class on behalf of the async_scoped_session class.

Proxied for the Session class on behalf of the AsyncSession class.

See the documentation for Session.add() for a general behavioral description.

See also

Session.add()

Adding New or Existing Items - at Basics of Using a Session

attribute sqlalchemy.ext.asyncio.async_scoped_session.autoflush

Proxied for the AsyncSession class on behalf of the async_scoped_session class.

method sqlalchemy.ext.asyncio.async_scoped_session.begin(**kw)

Return an AsyncSessionTransaction object.

Proxied for the AsyncSession class on behalf of the async_scoped_session class.

The underlying Session will perform the “begin” action when the AsyncSessionTransaction object is entered:

async with async_session.begin():
    # .. ORM transaction is begun

Note that database IO will not normally occur when the session-level transaction is begun, as database transactions begin on an on-demand basis. However, the begin block is async to accommodate for a 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(**kw)

Return an AsyncSessionTransaction object which will begin a “nested” transaction, e.g. SAVEPOINT.

Proxied for the AsyncSession class on behalf of the async_scoped_session class.

Behavior is the same as that of AsyncSession.begin().

For a general description of ORM begin nested, see Session.begin_nested().

method sqlalchemy.ext.asyncio.async_scoped_session.close()

Close out the transactional resources and ORM objects used by this AsyncSession.

Proxied for the AsyncSession class on behalf of the async_scoped_session class.

This expunges all ORM objects associated with this AsyncSession, ends any transaction in progress and releases any AsyncConnection objects which this AsyncSession itself has checked out from associated AsyncEngine objects. The operation then leaves the AsyncSession in a state which it may be used again.

Tip

The AsyncSession.close() method does not prevent the Session from being used again. The AsyncSession itself does not actually have a distinct “closed” state; it merely means the AsyncSession will release all database connections and ORM objects.

See also

Closing - detail on the semantics of AsyncSession.close()

classmethod sqlalchemy.ext.asyncio.async_scoped_session.close_all()

Close all AsyncSession sessions.

Proxied for the AsyncSession class on behalf of the async_scoped_session class.

method sqlalchemy.ext.asyncio.async_scoped_session.commit()

Commit the current transaction in progress.

Proxied for the AsyncSession class on behalf of the async_scoped_session class.

method sqlalchemy.ext.asyncio.async_scoped_session.configure(**kwargs)

inherited from the ScopedSessionMixin.configure() method of ScopedSessionMixin

reconfigure the sessionmaker used by this scoped_session.

See sessionmaker.configure().

method sqlalchemy.ext.asyncio.async_scoped_session.connection(**kw)

Return a AsyncConnection object corresponding to this Session object’s transactional state.

Proxied for the AsyncSession class on behalf of the async_scoped_session class.

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.delete(instance)

Mark an instance as deleted.

Proxied for the AsyncSession class on behalf of the async_scoped_session class.

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 Session

Proxied for the AsyncSession class on behalf of the async_scoped_session class.

Proxied for the Session class on behalf of the AsyncSession class.

attribute sqlalchemy.ext.asyncio.async_scoped_session.dirty

The set of all persistent instances considered dirty.

Proxied for the AsyncSession class on behalf of the async_scoped_session class.

Proxied for the Session class on behalf of the AsyncSession class.

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.execute(statement, params=None, execution_options={}, bind_arguments=None, **kw)

Execute a statement and return a buffered Result object.

Proxied for the AsyncSession class on behalf of the async_scoped_session class.

See also

Session.execute() - main documentation for execute

method sqlalchemy.ext.asyncio.async_scoped_session.expire(instance, attribute_names=None)

Expire the attributes on an instance.

Proxied for the AsyncSession class on behalf of the async_scoped_session class.

Proxied for the Session class on behalf of the AsyncSession class.

Marks the attributes of an instance as out of date. When an expired attribute is next accessed, a query will be issued to the Session object’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 Session simultaneously, use Session.expire_all().

The Session object’s default behavior is to expire all state whenever the Session.rollback() or Session.commit() methods are called, so that new state can be loaded for the new transaction. For this reason, calling Session.expire() only makes sense for the specific case that a non-ORM SQL statement was emitted in the current transaction.

Parameters:

• instance – The instance to be refreshed.

• attribute_names – optional list of string attribute names indicating a subset of attributes to be expired.

See also

Refreshing / Expiring - introductory material

Session.expire()

Session.refresh()

Query.populate_existing()

method sqlalchemy.ext.asyncio.async_scoped_session.expire_all()

Expires all persistent instances within this Session.

Proxied for the AsyncSession class on behalf of the async_scoped_session class.

Proxied for the Session class on behalf of the AsyncSession class.

When any attributes on a persistent instance is next accessed, a query will be issued using the Session object’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 Session object’s default behavior is to expire all state whenever the Session.rollback() or Session.commit() methods are called, so that new state can be loaded for the new transaction. For this reason, calling Session.expire_all() should not be needed when autocommit is False, assuming the transaction is isolated.

See also

Refreshing / Expiring - introductory material

Session.expire()

Session.refresh()

Query.populate_existing()

method sqlalchemy.ext.asyncio.async_scoped_session.expunge(instance)

Remove the instance from this Session.

Proxied for the AsyncSession class on behalf of the async_scoped_session class.

Proxied for the Session class on behalf of the AsyncSession class.

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()

Remove all object instances from this Session.

Proxied for the AsyncSession class on behalf of the async_scoped_session class.

Proxied for the Session class on behalf of the AsyncSession class.

This is equivalent to calling expunge(obj) on all objects in this Session.

method sqlalchemy.ext.asyncio.async_scoped_session.flush(objects=None)

Flush all the object changes to the database.

Proxied for the AsyncSession class on behalf of the async_scoped_session class.

See also

Session.flush() - main documentation for flush

method sqlalchemy.ext.asyncio.async_scoped_session.get(entity, ident, options=None, populate_existing=False, with_for_update=None, identity_token=None)

Return an instance based on the given primary key identifier, or None if not found.

Proxied for the AsyncSession class on behalf of the async_scoped_session class.

See also

Session.get() - main documentation for get

method sqlalchemy.ext.asyncio.async_scoped_session.get_bind(mapper=None, clause=None, bind=None, **kw)

Return a “bind” to which the synchronous proxied Session is bound.

Proxied for the AsyncSession class on behalf of the async_scoped_session class.

Unlike the Session.get_bind() method, this method is currently not used by this AsyncSession in 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 the Session.get_bind() method. The example below illustrates how to implement custom Session.get_bind() schemes that work with AsyncSession and AsyncEngine.

The pattern introduced at Custom Vertical Partitioning illustrates how to apply a custom bind-lookup scheme to a Session given a set of Engine objects. To apply a corresponding Session.get_bind() implementation for use with a AsyncSession and AsyncEngine objects, continue to subclass Session and apply it to AsyncSession using AsyncSession.sync_session_class. The inner method must continue to return Engine instances, which can be acquired from a AsyncEngine using the AsyncEngine.sync_engine attribute:

# using example from "Custom Vertical Partitioning"


import random

from sqlalchemy.ext.asyncio import AsyncSession
from sqlalchemy.ext.asyncio import create_async_engine
from sqlalchemy.orm import Session, sessionmaker

# construct async engines w/ async drivers
engines = {
    'leader':create_async_engine("sqlite+aiosqlite:///leader.db"),
    'other':create_async_engine("sqlite+aiosqlite:///other.db"),
    'follower1':create_async_engine("sqlite+aiosqlite:///follower1.db"),
    'follower2':create_async_engine("sqlite+aiosqlite:///follower2.db"),
}

class RoutingSession(Session):
    def get_bind(self, mapper=None, clause=None, **kw):
        # within get_bind(), return sync engines
        if mapper and issubclass(mapper.class_, MyOtherClass):
            return engines['other'].sync_engine
        elif self._flushing or isinstance(clause, (Update, Delete)):
            return engines['leader'].sync_engine
        else:
            return engines[
                random.choice(['follower1','follower2'])
            ].sync_engine

# apply to AsyncSession using sync_session_class
AsyncSessionMaker = sessionmaker(
    class_=AsyncSession,
    sync_session_class=RoutingSession
)

The Session.get_bind() method is called in a non-asyncio, implicitly non-blocking context in the same manner as ORM event hooks and functions that are invoked via AsyncSession.run_sync(), so routines that wish to run SQL commands inside of Session.get_bind() can continue to do so using blocking-style code, which will be translated to implicitly async calls at the point of invoking IO on the database drivers.

classmethod sqlalchemy.ext.asyncio.async_scoped_session.identity_key(*args, **kwargs)

Return an identity key.

Proxied for the AsyncSession class on behalf of the async_scoped_session class.

Proxied for the Session class on behalf of the AsyncSession class.

This is an alias of identity_key().

attribute sqlalchemy.ext.asyncio.async_scoped_session.identity_map

Proxied for the AsyncSession class on behalf of the async_scoped_session class.

attribute sqlalchemy.ext.asyncio.async_scoped_session.info

A user-modifiable dictionary.

Proxied for the AsyncSession class on behalf of the async_scoped_session class.

Proxied for the Session class on behalf of the AsyncSession class.

The initial value of this dictionary can be populated using the info argument to the Session constructor or sessionmaker constructor or factory methods. The dictionary here is always local to this Session and can be modified independently of all other Session objects.

method sqlalchemy.ext.asyncio.async_scoped_session.invalidate()

Close this Session, using connection invalidation.

Proxied for the AsyncSession class on behalf of the async_scoped_session class.

For a complete description, see Session.invalidate().

attribute sqlalchemy.ext.asyncio.async_scoped_session.is_active

True if this Session not in “partial rollback” state.

Proxied for the AsyncSession class on behalf of the async_scoped_session class.

Proxied for the Session class on behalf of the AsyncSession class.

Changed in version 1.4: The Session no longer begins a new transaction immediately, so this attribute will be False when the Session is first instantiated.

“partial rollback” state typically indicates that the flush process of the Session has failed, and that the Session.rollback() method must be emitted in order to fully roll back the transaction.

If this Session is not in a transaction at all, the Session will autobegin when it is first used, so in this case Session.is_active will return True.

Otherwise, if this Session is within a transaction, and that transaction has not been rolled back internally, the Session.is_active will also return True.

See also

“This Session’s transaction has been rolled back due to a previous exception during flush.” (or similar)

Session.in_transaction()

method sqlalchemy.ext.asyncio.async_scoped_session.is_modified(instance, include_collections=True)

Return True if the given instance has locally modified attributes.

Proxied for the AsyncSession class on behalf of the async_scoped_session class.

Proxied for the Session class on behalf of the AsyncSession class.

This method retrieves the history for each instrumented attribute on the instance and performs a comparison of the current value to its previously committed value, if any.

It is in effect a more expensive and accurate version of checking for the given instance in the Session.dirty collection; 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.dirty collection may report False when tested with this method. This is because the object may have received change events via attribute mutation, thus placing it in Session.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_history flag set to True. 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 the active_history argument with column_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 False is 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.merge(instance, load=True, options=None)

Copy the state of a given instance into a corresponding instance within this AsyncSession.

Proxied for the AsyncSession class on behalf of the async_scoped_session class.

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 AsyncSession class on behalf of the async_scoped_session class.

Proxied for the Session class on behalf of the AsyncSession class.

attribute sqlalchemy.ext.asyncio.async_scoped_session.no_autoflush

Return a context manager that disables autoflush.

Proxied for the AsyncSession class on behalf of the async_scoped_session class.

Proxied for the Session class on behalf of the AsyncSession class.

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)

Return the Session to which an object belongs.

Proxied for the AsyncSession class on behalf of the async_scoped_session class.

Proxied for the Session class on behalf of the AsyncSession class.

This is an alias of object_session().

method sqlalchemy.ext.asyncio.async_scoped_session.refresh(instance, attribute_names=None, with_for_update=None)

Expire and refresh the attributes on the given instance.

Proxied for the AsyncSession class on behalf of the async_scoped_session class.

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()

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.rollback()

Rollback the current transaction in progress.

Proxied for the AsyncSession class on behalf of the async_scoped_session class.

method sqlalchemy.ext.asyncio.async_scoped_session.scalar(statement, params=None, execution_options={}, bind_arguments=None, **kw)

Execute a statement and return a scalar result.

Proxied for the AsyncSession class on behalf of the async_scoped_session class.

See also

Session.scalar() - main documentation for scalar

method sqlalchemy.ext.asyncio.async_scoped_session.scalars(statement, params=None, execution_options={}, bind_arguments=None, **kw)

Execute a statement and return scalar results.

Proxied for the AsyncSession class on behalf of the async_scoped_session class.

Returns:

a ScalarResult object

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 scalars

AsyncSession.stream_scalars() - streaming version

method sqlalchemy.ext.asyncio.async_scoped_session.stream(statement, params=None, execution_options={}, bind_arguments=None, **kw)

Execute a statement and return a streaming AsyncResult object.

Proxied for the AsyncSession class on behalf of the async_scoped_session class.

method sqlalchemy.ext.asyncio.async_scoped_session.stream_scalars(statement, params=None, execution_options={}, bind_arguments=None, **kw)

Execute a statement and return a stream of scalar results.

Proxied for the AsyncSession class on behalf of the async_scoped_session class.

Returns:

an AsyncScalarResult object

New in version 1.4.24.

See also

Session.scalars() - main documentation for scalars

AsyncSession.scalars() - non streaming version

class sqlalchemy.ext.asyncio.AsyncSession(bind=None, binds=None, sync_session_class=None, **kw)

Asyncio version of Session.

The AsyncSession is a proxy for a traditional Session instance.

New in version 1.4.

To use an AsyncSession with custom Session implementations, see the AsyncSession.sync_session_class parameter.

Members

sync_session_class, __init__(), add(), add_all(), 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_transaction(), identity_key(), in_nested_transaction(), in_transaction(), info, invalidate(), is_active, is_modified(), merge(), new, no_autoflush, object_session(), refresh(), 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 = <class 'sqlalchemy.orm.session.Session'>

The class or callable that provides the underlying Session instance for a particular AsyncSession.

At the class level, this attribute is the default value for the AsyncSession.sync_session_class parameter. Custom subclasses of AsyncSession can override this.

At the instance level, this attribute indicates the current class or callable that was used to provide the Session instance for this AsyncSession instance.

New in version 1.4.24.

method sqlalchemy.ext.asyncio.AsyncSession.__init__(bind=None, binds=None, sync_session_class=None, **kw)

Construct a new AsyncSession.

All parameters other than sync_session_class are passed to the sync_session_class callable directly to instantiate a new Session. Refer to Session.__init__() for parameter documentation.

Parameters:

sync_session_class –

A Session subclass or other callable which will be used to construct the Session which will be proxied. This parameter may be used to provide custom Session subclasses. Defaults to the AsyncSession.sync_session_class class-level attribute.

New in version 1.4.24.

method sqlalchemy.ext.asyncio.AsyncSession.add(instance, _warn=True)

Place an object into this Session.

Proxied for the Session class on behalf of the AsyncSession class.

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 Session is rolled back, objects which were transient when they were passed to Session.add() will be moved back to the transient state, and will no longer be present within this Session.

See also

Session.add_all()

Adding New or Existing Items - at Basics of Using a Session

method sqlalchemy.ext.asyncio.AsyncSession.add_all(instances)

Add the given collection of instances to this Session.

Proxied for the Session class on behalf of the AsyncSession class.

See the documentation for Session.add() for a general behavioral description.

See also

Session.add()

Adding New or Existing Items - at Basics of Using a Session

method sqlalchemy.ext.asyncio.AsyncSession.begin(**kw)

Return an AsyncSessionTransaction object.

The underlying Session will perform the “begin” action when the AsyncSessionTransaction object is entered:

async with async_session.begin():
    # .. ORM transaction is begun

Note that database IO will not normally occur when the session-level transaction is begun, as database transactions begin on an on-demand basis. However, the begin block is async to accommodate for a 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(**kw)

Return an AsyncSessionTransaction object 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().

method sqlalchemy.ext.asyncio.AsyncSession.async close()

Close out the transactional resources and ORM objects used by this AsyncSession.

This expunges all ORM objects associated with this AsyncSession, ends any transaction in progress and releases any AsyncConnection objects which this AsyncSession itself has checked out from associated AsyncEngine objects. The operation then leaves the AsyncSession in a state which it may be used again.

Tip

The AsyncSession.close() method does not prevent the Session from being used again. The AsyncSession itself does not actually have a distinct “closed” state; it merely means the AsyncSession will release all database connections and ORM objects.

See also

Closing - detail on the semantics of AsyncSession.close()

async classmethod sqlalchemy.ext.asyncio.AsyncSession.close_all()

Close all AsyncSession sessions.

method sqlalchemy.ext.asyncio.AsyncSession.async commit()

Commit the current transaction in progress.

method sqlalchemy.ext.asyncio.AsyncSession.async connection(**kw)

Return a AsyncConnection object corresponding to this Session object’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)

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 Session

Proxied for the Session class on behalf of the AsyncSession class.

attribute sqlalchemy.ext.asyncio.AsyncSession.dirty

The set of all persistent instances considered dirty.

Proxied for the Session class on behalf of the AsyncSession class.

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, params=None, execution_options={}, bind_arguments=None, **kw)

Execute a statement and return a buffered Result object.

See also

Session.execute() - main documentation for execute

method sqlalchemy.ext.asyncio.AsyncSession.expire(instance, attribute_names=None)

Expire the attributes on an instance.

Proxied for the Session class on behalf of the AsyncSession class.

Marks the attributes of an instance as out of date. When an expired attribute is next accessed, a query will be issued to the Session object’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 Session simultaneously, use Session.expire_all().

The Session object’s default behavior is to expire all state whenever the Session.rollback() or Session.commit() methods are called, so that new state can be loaded for the new transaction. For this reason, calling Session.expire() only makes sense for the specific case that a non-ORM SQL statement was emitted in the current transaction.

Parameters:

• instance – The instance to be refreshed.

• attribute_names – optional list of string attribute names indicating a subset of attributes to be expired.

See also

Refreshing / Expiring - introductory material

Session.expire()

Session.refresh()

Query.populate_existing()

method sqlalchemy.ext.asyncio.AsyncSession.expire_all()

Expires all persistent instances within this Session.

Proxied for the Session class on behalf of the AsyncSession class.

When any attributes on a persistent instance is next accessed, a query will be issued using the Session object’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 Session object’s default behavior is to expire all state whenever the Session.rollback() or Session.commit() methods are called, so that new state can be loaded for the new transaction. For this reason, calling Session.expire_all() should not be needed when autocommit is False, assuming the transaction is isolated.

See also

Refreshing / Expiring - introductory material

Session.expire()

Session.refresh()

Query.populate_existing()

method sqlalchemy.ext.asyncio.AsyncSession.expunge(instance)

Remove the instance from this Session.

Proxied for the Session class on behalf of the AsyncSession class.

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()

Remove all object instances from this Session.

Proxied for the Session class on behalf of the AsyncSession class.

This is equivalent to calling expunge(obj) on all objects in this Session.

method sqlalchemy.ext.asyncio.AsyncSession.async flush(objects=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, ident, options=None, populate_existing=False, with_for_update=None, identity_token=None)

Return an instance based on the given primary key identifier, or None if not found.

See also

Session.get() - main documentation for get

method sqlalchemy.ext.asyncio.AsyncSession.get_bind(mapper=None, clause=None, bind=None, **kw)

Return a “bind” to which the synchronous proxied Session is bound.

Unlike the Session.get_bind() method, this method is currently not used by this AsyncSession in 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 the Session.get_bind() method. The example below illustrates how to implement custom Session.get_bind() schemes that work with AsyncSession and AsyncEngine.

The pattern introduced at Custom Vertical Partitioning illustrates how to apply a custom bind-lookup scheme to a Session given a set of Engine objects. To apply a corresponding Session.get_bind() implementation for use with a AsyncSession and AsyncEngine objects, continue to subclass Session and apply it to AsyncSession using AsyncSession.sync_session_class. The inner method must continue to return Engine instances, which can be acquired from a AsyncEngine using the AsyncEngine.sync_engine attribute:

# using example from "Custom Vertical Partitioning"


import random

from sqlalchemy.ext.asyncio import AsyncSession
from sqlalchemy.ext.asyncio import create_async_engine
from sqlalchemy.orm import Session, sessionmaker

# construct async engines w/ async drivers
engines = {
    'leader':create_async_engine("sqlite+aiosqlite:///leader.db"),
    'other':create_async_engine("sqlite+aiosqlite:///other.db"),
    'follower1':create_async_engine("sqlite+aiosqlite:///follower1.db"),
    'follower2':create_async_engine("sqlite+aiosqlite:///follower2.db"),
}

class RoutingSession(Session):
    def get_bind(self, mapper=None, clause=None, **kw):
        # within get_bind(), return sync engines
        if mapper and issubclass(mapper.class_, MyOtherClass):
            return engines['other'].sync_engine
        elif self._flushing or isinstance(clause, (Update, Delete)):
            return engines['leader'].sync_engine
        else:
            return engines[
                random.choice(['follower1','follower2'])
            ].sync_engine

# apply to AsyncSession using sync_session_class
AsyncSessionMaker = sessionmaker(
    class_=AsyncSession,
    sync_session_class=RoutingSession
)

The Session.get_bind() method is called in a non-asyncio, implicitly non-blocking context in the same manner as ORM event hooks and functions that are invoked via AsyncSession.run_sync(), so routines that wish to run SQL commands inside of Session.get_bind() can continue to do so using blocking-style code, which will be translated to implicitly async calls at the point of invoking IO on the database drivers.

method sqlalchemy.ext.asyncio.AsyncSession.get_nested_transaction()

Return the current nested transaction in progress, if any.

Returns:

an AsyncSessionTransaction object, or None.

New in version 1.4.18.

method sqlalchemy.ext.asyncio.AsyncSession.get_transaction()

Return the current root transaction in progress, if any.

Returns:

an AsyncSessionTransaction object, or None.

New in version 1.4.18.

classmethod sqlalchemy.ext.asyncio.AsyncSession.identity_key(*args, **kwargs)

Return an identity key.

Proxied for the Session class on behalf of the AsyncSession class.

This is an alias of identity_key().

method sqlalchemy.ext.asyncio.AsyncSession.in_nested_transaction()

Return True if this Session has begun a nested transaction, e.g. SAVEPOINT.

Proxied for the Session class on behalf of the AsyncSession class.

New in version 1.4.

method sqlalchemy.ext.asyncio.AsyncSession.in_transaction()

Return True if this Session has begun a transaction.

Proxied for the Session class on behalf of the AsyncSession class.

New in version 1.4.

See also

Session.is_active

attribute sqlalchemy.ext.asyncio.AsyncSession.info

A user-modifiable dictionary.

Proxied for the Session class on behalf of the AsyncSession class.

The initial value of this dictionary can be populated using the info argument to the Session constructor or sessionmaker constructor or factory methods. The dictionary here is always local to this Session and can be modified independently of all other Session objects.

method sqlalchemy.ext.asyncio.AsyncSession.async invalidate()

Close this Session, using connection invalidation.

For a complete description, see Session.invalidate().

attribute sqlalchemy.ext.asyncio.AsyncSession.is_active

True if this Session not in “partial rollback” state.

Proxied for the Session class on behalf of the AsyncSession class.

Changed in version 1.4: The Session no longer begins a new transaction immediately, so this attribute will be False when the Session is first instantiated.

“partial rollback” state typically indicates that the flush process of the Session has failed, and that the Session.rollback() method must be emitted in order to fully roll back the transaction.

If this Session is not in a transaction at all, the Session will autobegin when it is first used, so in this case Session.is_active will return True.

Otherwise, if this Session is within a transaction, and that transaction has not been rolled back internally, the Session.is_active will also return True.

See also

“This Session’s transaction has been rolled back due to a previous exception during flush.” (or similar)

Session.in_transaction()

method sqlalchemy.ext.asyncio.AsyncSession.is_modified(instance, include_collections=True)

Return True if the given instance has locally modified attributes.

Proxied for the Session class on behalf of the AsyncSession class.

This method retrieves the history for each instrumented attribute on the instance and performs a comparison of the current value to its previously committed value, if any.

It is in effect a more expensive and accurate version of checking for the given instance in the Session.dirty collection; 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.dirty collection may report False when tested with this method. This is because the object may have received change events via attribute mutation, thus placing it in Session.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_history flag set to True. 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 the active_history argument with column_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 False is 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, load=True, options=None)

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 Session class on behalf of the AsyncSession class.

attribute sqlalchemy.ext.asyncio.AsyncSession.no_autoflush

Return a context manager that disables autoflush.

Proxied for the Session class on behalf of the AsyncSession class.

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)

Return the Session to which an object belongs.

Proxied for the Session class on behalf of the AsyncSession class.

This is an alias of object_session().

method sqlalchemy.ext.asyncio.AsyncSession.async refresh(instance, attribute_names=None, with_for_update=None)

Expire and refresh the attributes on the given instance.

A query will be issued to the database and all attributes will be refreshed with their current database value.

This is the async version of the 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 rollback()

Rollback the current transaction in progress.

method sqlalchemy.ext.asyncio.AsyncSession.async run_sync(fn, *arg, **kw)

Invoke the given sync callable passing sync self as the first argument.

This method maintains the asyncio event loop all the way through to the database connection by running the given callable in a specially instrumented greenlet.

E.g.:

with AsyncSession(async_engine) as session:
    await session.run_sync(some_business_method)

Note

The provided callable is invoked inline within the asyncio event loop, and will block on traditional IO calls. IO within this callable should only call into SQLAlchemy’s asyncio database APIs which will be properly adapted to the greenlet context.

See also

Running Synchronous Methods and Functions under asyncio

method sqlalchemy.ext.asyncio.AsyncSession.async scalar(statement, params=None, execution_options={}, bind_arguments=None, **kw)

Execute a statement and return a scalar result.

See also

Session.scalar() - main documentation for scalar

method sqlalchemy.ext.asyncio.AsyncSession.async scalars(statement, params=None, execution_options={}, bind_arguments=None, **kw)

Execute a statement and return scalar results.

Returns:

a ScalarResult object

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 scalars

AsyncSession.stream_scalars() - streaming version

method sqlalchemy.ext.asyncio.AsyncSession.async stream(statement, params=None, execution_options={}, bind_arguments=None, **kw)

Execute a statement and return a streaming AsyncResult object.

method sqlalchemy.ext.asyncio.AsyncSession.async stream_scalars(statement, params=None, execution_options={}, bind_arguments=None, **kw)

Execute a statement and return a stream of scalar results.

Returns:

an AsyncScalarResult object

New in version 1.4.24.

See also

Session.scalars() - main documentation for scalars

AsyncSession.scalars() - non streaming version

attribute sqlalchemy.ext.asyncio.AsyncSession.sync_session: Session

Reference to the underlying Session this AsyncSession proxies requests towards.

This instance can be used as an event target.

See also

Using events with the asyncio extension

class sqlalchemy.ext.asyncio.AsyncSessionTransaction(session, nested=False)

A wrapper for the ORM SessionTransaction object.

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() and AsyncSessionTransaction.rollback(), as well as use as an async context manager.

New in version 1.4.

Members

commit(), rollback()

Class signature

class sqlalchemy.ext.asyncio.AsyncSessionTransaction (sqlalchemy.ext.asyncio.base.ReversibleProxy, sqlalchemy.ext.asyncio.base.StartableContext)

method sqlalchemy.ext.asyncio.AsyncSessionTransaction.async commit()

Commit this AsyncTransaction.

method sqlalchemy.ext.asyncio.AsyncSessionTransaction.async rollback()

Roll back this AsyncTransaction.