Contextual/Thread-local Sessions¶

When do I construct a Session, when do I commit it, and when do I close it? の節で、”セッションスコープ”の概念が導入され、Webアプリケーションと Session のスコープをWebリクエストのスコープにリンクすることに重点が置かれたことを思い出してください。最近のWebフレームワークのほとんどには、 Session のスコープを自動的に管理できるように統合ツールが含まれており、これらのツールは利用可能な状態で使用する必要があります。

SQLAlchemyには独自のヘルパーオブジェクトが含まれており、ユーザ定義の Session スコープの確立を支援します。また、サードパーティの統合システムでは、統合スキームの構築を支援するために使用されます。

このオブジェクトは scoped_session オブジェクトで、 Session オブジェクトの レジストリ を表します。レジストリパターンに詳しくない場合は、 Patterns of Enterprise Architecture を参照してください。

Warning

scoped_session レジストリはデフォルトで、 Session インスタンスを追跡するためにPythonの threading.local() を使用します。 これはすべてのアプリケーションサーバ と必ずしも互換性があるとは限りません。特に、グリーンレットやその他の代替形式の同時実行制御を使用しているサーバでは、中程度から高度の同時実行シナリオで使用すると、競合状態(例えば、ランダムに発生する障害)につながる可能性があります。 Session オブジェクトを追跡するために threading.local() を使用することの意味をより十分に理解するために、以下の Thread-Local Scope と Using Thread-Local Scope with Web Applications を読んでください。また、従来のスレッドに基づいていないアプリケーションサーバを使用する場合には、より明示的なスコープ手段を検討してください。

Note

scoped_session オブジェクトは、多くのSQLAlchemyアプリケーションで使用されている非常に一般的で便利なオブジェクトです。しかし、 Session 管理の問題に対して 唯一のアプローチ を提供していることに注意してください。SQLAlchemyを初めて使用する場合、特に”スレッドローカル変数”という用語が奇妙に思える場合は、可能であればまず Flask-SQLAlchemy や zope.SQLAlchemy などの既製の統合システムに慣れておくことをお勧めします。

scoped_session は、それを呼び出し、新しい Session オブジェクトを作成できる factory を渡すことによって構築されます。ファクトリは、呼び出されたときに新しいオブジェクトを生成するものです。 Session の場合、最も一般的なファクトリは、このセクションの前半で紹介した sessionmaker です。以下で、この使用法を説明します:

>>> from sqlalchemy.orm import scoped_session
>>> from sqlalchemy.orm import sessionmaker

>>> session_factory = sessionmaker(bind=some_engine)
>>> Session = scoped_session(session_factory)

作成した scoped_session オブジェクトは、レジストリを”呼び出す”ときに sessionmaker を呼び出します:

>>> some_session = Session()

上記では、 some_session は Session のインスタンスで、これを使ってデータベースと対話できます。これと同じ Session は、作成した scoped_session レジストリ内にも存在します。レジストリをもう一度呼び出すと、同じ Session が返されます:

>>> some_other_session = Session()
>>> some_session is some_other_session
True

このパターンでは、アプリケーションの異なるセクションがグローバルな scoped_session を呼び出すことができるので、それらのすべての領域が明示的に渡さなくても同じセッションを共有することができます。レジストリで確立した Session は、 scoped_session.remove() を呼び出して、レジストリに明示的に破棄するように指示するまで残ります:

>>> Session.remove()

scoped_session.remove() メソッドは、まず現在の Session に対して Session.close() を呼び出します。これは、まず Session が所有する接続/トランザクションリソースを解放し、次に Session 自体を破棄する効果があります。ここでの”解放”とは、接続が接続プールに戻され、トランザクション状態がロールバックされることを意味します。最終的には、基礎となるDBAPI接続の rollback() メソッドを使用します。

この時点で、 scoped_session オブジェクトは”空”であり、再度呼び出されると 新しい Session を作成します。以下に示すように、これは以前と同じ Session ではありません:

>>> new_session = Session()
>>> new_session is some_session
False

上記の一連のステップは、”registry”パターンの概念を簡単に説明したものです。この基本的な考え方を理解した上で、このパターンがどのように進行するかについて詳しく説明します。

Implicit Method Access¶

scoped_session の仕事は単純です。 Session を要求するすべての人のために保持します。この Session へのより透過的なアクセスを生成する手段として、 scoped_session には プロキシ動作 も含まれています。これは、レジストリ自体を Session のように直接扱うことができることを意味します。このオブジェクトでメソッドが呼び出されると、それらはレジストリによって維持されている基礎となる Session に プロキシ されます:

Session = scoped_session(some_factory)

# equivalent to:
#
# session = Session()
# print(session.scalars(select(MyClass)).all())
#
print(Session.scalars(select(MyClass)).all())

上記のコードは、レジストリを呼び出してからその Session を使用することで、現在の Session を取得するのと同じタスクを実行します。

Thread-Local Scope¶

マルチスレッドプログラミングに精通しているユーザは、グローバル変数として何かを表現することは、多くのスレッドが同時にグローバルオブジェクトにアクセスすることを意味するので、通常は悪い考えであることに気づくでしょう。 Session オブジェクトは、 非同時 な方法で使用されるように完全に設計されています。マルチスレッドの観点からは、これは”一度に1つのスレッドのみ”を意味します。したがって、上記の scoped_session の使用例では、同じ Session オブジェクトが複数の呼び出しにわたって維持されていますが、これは、多くのスレッドにまたがる複数の呼び出しが実際には同じセッションへのハンドルを取得しないように、何らかのプロセスを配置する必要があることを示唆しています。この概念を スレッドローカルストレージ と呼びます。これは、各アプリケーションスレッドごとに異なるオブジェクトを維持する特別なオブジェクトが使用されることを意味します。Pythonはこれを threading.local() 構成体を介して提供します。 scoped_session オブジェクトはデフォルトでこのオブジェクトをストレージとして使用するので、 scoped_session レジストリを呼び出すすべての人に対して単一の Session が維持されますが、単一のスレッドのスコープ内でのみです。別のスレッドのレジストリを呼び出す呼び出し元は、その他のスレッドに対してローカルな Session インスタンスを取得します。

このテクニックを使うことで、 scoped_session は、複数のスレッドから安全に呼び出すことができる単一のグローバルオブジェクトをアプリケーション内に提供する、速くて比較的簡単な方法を提供します(スレッドローカルストレージに精通している場合)。

scoped_session.remove() メソッドは、いつものように、スレッドに関連付けられた現在の Session を削除します。ただし、 threading.local() オブジェクトの利点の1つは、アプリケーションスレッド自体が終了した場合、そのスレッドの”ストレージ”もガベージコレクションされることです。そのため、スレッドを生成してティアダウンするアプリケーションでは、 scoped_session.remove() を呼び出すことなく、スレッドのローカルスコープを使用しても”安全”です。ただし、トランザクション自体のスコープ、つまり Session.commit() または Session.rollback() で終了するスコープは、アプリケーションが実際にスレッドの寿命とトランザクションの寿命を結び付けない限り、通常は適切な時点で明示的に準備する必要があります。

Using Thread-Local Scope with Web Applications¶

When do I construct a Session, when do I commit it, and when do I close it? セクションで説明したように、Webアプリケーションは Webリクエスト の概念を中心に構築されており、このようなアプリケーションを Session と統合することは、通常、 Session がそのリクエストに関連付けられることを意味します。結局のところ、ほとんどのPython Webフレームワークは、非同期フレームワークのTwistedやTornadoなどの顕著な例外を除いて、特定のWebリクエストが単一の worker thread のスコープ内で受信、処理、完了されるように、単純な方法でスレッドを使用しています。リクエストが終了すると、ワーカースレッドはワーカーのプールに解放され、別のリクエストを処理できるようになります。

Web要求とスレッドがこのように単純に対応しているということは、 Session をスレッドに関連付けるということは、そのスレッドがそのスレッド内で実行されているWeb要求にも関連付けられていることを意味します。逆もまた同様です。ただし、 Session はWeb要求の開始後にのみ作成され、Web要求が終了する直前に破棄されます。そのため、 Session をWebアプリケーションに簡単に統合する方法として、 scoped_session を使用するのが一般的です。次のシーケンス図は、この流れを示しています。

Web Server          Web Framework        SQLAlchemy ORM Code
--------------      --------------       ------------------------------
startup        ->   Web framework        # Session registry is established
                    initializes          Session = scoped_session(sessionmaker())

incoming
web request    ->   web request     ->   # The registry is *optionally*
                    starts               # called upon explicitly to create
                                         # a Session local to the thread and/or request
                                         Session()

                                         # the Session registry can otherwise
                                         # be used at any time, creating the
                                         # request-local Session() if not present,
                                         # or returning the existing one
                                         Session.execute(select(MyClass)) # ...

                                         Session.add(some_object) # ...

                                         # if data was modified, commit the
                                         # transaction
                                         Session.commit()

                    web request ends  -> # the registry is instructed to
                                         # remove the Session
                                         Session.remove()

                    sends output      <-
outgoing web    <-
response

上記のフローを使用して、 Session をWebアプリケーションと統合するプロセスには、次の2つの要件があります。:

Webアプリケーションの最初の起動時に単一の scoped_session レジストリを作成し、このオブジェクトがアプリケーションの残りの部分からアクセスできるようにします。

Web要求が終了したときに scoped_session.remove() が呼び出されるようにします。これは通常、Webフレームワークのイベントシステムと統合して”要求終了時”イベントを確立することによって行います。

前述したように、上記のパターンは、Webフレームワークと Session を統合する 1つの方法 にすぎず、特に WebフレームワークがWebリクエストをアプリケーションスレッドに関連付ける という重要な前提を置いています。しかし 可能であれば、 :class:`.scoped_session` の代わりに、Webフレームワーク自体に用意されている統合ツールを使用することを強くお勧めします。

特に、スレッドローカルを使用すると便利ですが、 Session を現在のスレッドではなく、 直接リクエスト に関連付けることが望ましいです。カスタムスコープに関する次のセクションでは、 scoped_session の使用を直接リクエストベースのスコープ、または任意の種類のスコープと組み合わせることができる、より高度な設定について詳しく説明します。

Using Custom Created Scopes¶

scoped_session オブジェクトのデフォルトの振る舞いである”thread local”スコープは、 Session を”スコープ”する方法に関する多くのオプションの1つにすぎません。カスタムスコープは、”現在作業中のもの”を取得する既存のシステムに基づいて定義できます。

Webフレームワークがライブラリ関数 get_current_request() を定義しているとします。このフレームワークを使用して構築されたアプリケーションは、いつでもこの関数を呼び出すことができ、その結果は、処理されている現在の要求を表すある種の Request オブジェクトになります。 Request オブジェクトがハッシュ可能であれば、この関数を scoped_session と簡単に統合して、 Session を要求に関連付けることができます。以下では、これをWebフレームワーク on_request_end によって提供される仮想イベントマーカーと組み合わせて説明します。これにより、要求が終了するたびにコードを呼び出すことができます。:

from my_web_framework import get_current_request, on_request_end
from sqlalchemy.orm import scoped_session, sessionmaker

Session = scoped_session(sessionmaker(bind=some_engine), scopefunc=get_current_request)

@on_request_end
def remove_session(req):
    Session.remove()

上記では、通常の方法で scoped_session をインスタンス化しますが、リクエストを返す関数を”scopefunc”として渡します。これは scoped_session に、レジストリが現在の Session を返すために呼び出されるたびに、この関数を使用して辞書キーを生成するように指示します。この場合、この辞書は自己管理されていないので、信頼できる”削除”システムが実装されていることを確認することが特に重要です。

Contextual Session API¶

Object Name	Description
QueryPropertyDescriptor	Describes the type applied to a class-level `scoped_session.query_property()` attribute.
scoped_session	Provides scoped management of `Session` objects.
ScopedRegistry	A Registry that can store one or multiple instances of a single class on the basis of a “scope” function.
ThreadLocalRegistry	A `ScopedRegistry` that uses a `threading.local()` variable for storage.

class sqlalchemy.orm.scoped_session¶

Provides scoped management of Session objects.

See Contextual/Thread-local Sessions for a tutorial.

Note

When using Asynchronous I/O (asyncio), the async-compatible async_scoped_session class should be used in place of scoped_session.

Class signature

class sqlalchemy.orm.scoped_session (typing.Generic)

method sqlalchemy.orm.scoped_session.__call__(**kw: Any) → _S¶

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.orm.scoped_session.__init__(session_factory: sessionmaker[_S], scopefunc: Callable[[], Any] | None = None)¶

Construct a new scoped_session.

Parameters:

session_factory¶ – a factory to create new Session instances. This is usually, but not necessarily, an instance of sessionmaker.
scopefunc¶ – optional function which defines the current scope. If not passed, the scoped_session object assumes “thread-local” scope, and will use a Python threading.local() in order to maintain the current Session. If passed, the function should return a hashable token; this token will be used as the key in a dictionary in order to store and retrieve the current Session.

method sqlalchemy.orm.scoped_session.add(instance: object, _warn: bool = True) → None¶

Place an object into this Session.

Proxied for the Session class on behalf of the scoped_session 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.orm.scoped_session.add_all(instances: Iterable[object]) → None¶

Add the given collection of instances to this Session.

Proxied for the Session class on behalf of the scoped_session 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.orm.scoped_session.autoflush¶: Proxy for the Session.autoflush attribute on behalf of the scoped_session class.

method sqlalchemy.orm.scoped_session.begin(nested: bool = False) → SessionTransaction¶

Begin a transaction, or nested transaction, on this Session, if one is not already begun.

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

The Session object features autobegin behavior, so that normally it is not necessary to call the Session.begin() method explicitly. However, it may be used in order to control the scope of when the transactional state is begun.

When used to begin the outermost transaction, an error is raised if this Session is already inside of a transaction.

Parameters:: nested¶ – if True, begins a SAVEPOINT transaction and is equivalent to calling Session.begin_nested(). For documentation on SAVEPOINT transactions, please see Using SAVEPOINT.
Returns:: the SessionTransaction object. Note that SessionTransaction acts as a Python context manager, allowing Session.begin() to be used in a “with” block. See Explicit Begin for an example.

See also

Auto Begin

Managing Transactions

Session.begin_nested()

method sqlalchemy.orm.scoped_session.begin_nested() → SessionTransaction¶

Begin a “nested” transaction on this Session, e.g. SAVEPOINT.

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

The target database(s) and associated drivers must support SQL SAVEPOINT for this method to function correctly.

For documentation on SAVEPOINT transactions, please see Using SAVEPOINT.

Returns:: the SessionTransaction object. Note that SessionTransaction acts as a context manager, allowing Session.begin_nested() to be used in a “with” block. See Using SAVEPOINT for a usage example.

See also

Using SAVEPOINT

Serializable isolation / Savepoints / Transactional DDL - special workarounds required with the SQLite driver in order for SAVEPOINT to work correctly. For asyncio use cases, see the section Serializable isolation / Savepoints / Transactional DDL (asyncio version).

attribute sqlalchemy.orm.scoped_session.bind¶: Proxy for the Session.bind attribute on behalf of the scoped_session class.

method sqlalchemy.orm.scoped_session.bulk_insert_mappings(mapper: Mapper[Any], mappings: Iterable[Dict[str, Any]], return_defaults: bool = False, render_nulls: bool = False) → None¶

Perform a bulk insert of the given list of mapping dictionaries.

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

Legacy Feature

This method is a legacy feature as of the 2.0 series of SQLAlchemy. For modern bulk INSERT and UPDATE, see the sections ORM Bulk INSERT Statements and ORM Bulk UPDATE by Primary Key. The 2.0 API shares implementation details with this method and adds new features as well.

Parameters:

mapper¶ – a mapped class, or the actual Mapper object, representing the single kind of object represented within the mapping list.
mappings¶ – a sequence of dictionaries, each one containing the state of the mapped row to be inserted, in terms of the attribute names on the mapped class. If the mapping refers to multiple tables, such as a joined-inheritance mapping, each dictionary must contain all keys to be populated into all tables.
return_defaults¶ –
when True, the INSERT process will be altered to ensure that newly generated primary key values will be fetched. The rationale for this parameter is typically to enable Joined Table Inheritance mappings to be bulk inserted.

Note

for backends that don’t support RETURNING, the Session.bulk_insert_mappings.return_defaults parameter can significantly decrease performance as INSERT statements can no longer be batched. See “Insert Many Values” Behavior for INSERT statements for background on which backends are affected.
render_nulls¶ –
When True, a value of None will result in a NULL value being included in the INSERT statement, rather than the column being omitted from the INSERT. This allows all the rows being INSERTed to have the identical set of columns which allows the full set of rows to be batched to the DBAPI. Normally, each column-set that contains a different combination of NULL values than the previous row must omit a different series of columns from the rendered INSERT statement, which means it must be emitted as a separate statement. By passing this flag, the full set of rows are guaranteed to be batchable into one batch; the cost however is that server-side defaults which are invoked by an omitted column will be skipped, so care must be taken to ensure that these are not necessary.

Warning

When this flag is set, server side default SQL values will not be invoked for those columns that are inserted as NULL; the NULL value will be sent explicitly. Care must be taken to ensure that no server-side default functions need to be invoked for the operation as a whole.

Session.bulk_save_objects()

Session.bulk_update_mappings()

method sqlalchemy.orm.scoped_session.bulk_save_objects(objects: Iterable[object], return_defaults: bool = False, update_changed_only: bool = True, preserve_order: bool = True) → None¶

Perform a bulk save of the given list of objects.

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

Legacy Feature

This method is a legacy feature as of the 2.0 series of SQLAlchemy. For modern bulk INSERT and UPDATE, see the sections ORM Bulk INSERT Statements and ORM Bulk UPDATE by Primary Key.

For general INSERT and UPDATE of existing ORM mapped objects, prefer standard unit of work data management patterns, introduced in the SQLAlchemy Unified Tutorial at Data Manipulation with the ORM. SQLAlchemy 2.0 now uses “Insert Many Values” Behavior for INSERT statements with modern dialects which solves previous issues of bulk INSERT slowness.

Parameters:

objects¶ –
a sequence of mapped object instances. The mapped objects are persisted as is, and are not associated with the Session afterwards.

For each object, whether the object is sent as an INSERT or an UPDATE is dependent on the same rules used by the Session in traditional operation; if the object has the InstanceState.key attribute set, then the object is assumed to be “detached” and will result in an UPDATE. Otherwise, an INSERT is used.

In the case of an UPDATE, statements are grouped based on which attributes have changed, and are thus to be the subject of each SET clause. If update_changed_only is False, then all attributes present within each object are applied to the UPDATE statement, which may help in allowing the statements to be grouped together into a larger executemany(), and will also reduce the overhead of checking history on attributes.
return_defaults¶ – when True, rows that are missing values which generate defaults, namely integer primary key defaults and sequences, will be inserted one at a time, so that the primary key value is available. In particular this will allow joined-inheritance and other multi-table mappings to insert correctly without the need to provide primary key values ahead of time; however, Session.bulk_save_objects.return_defaults greatly reduces the performance gains of the method overall. It is strongly advised to please use the standard Session.add_all() approach.
update_changed_only¶ – when True, UPDATE statements are rendered based on those attributes in each state that have logged changes. When False, all attributes present are rendered into the SET clause with the exception of primary key attributes.
preserve_order¶ – when True, the order of inserts and updates matches exactly the order in which the objects are given. When False, common types of objects are grouped into inserts and updates, to allow for more batching opportunities.

Session.bulk_insert_mappings()

Session.bulk_update_mappings()

method sqlalchemy.orm.scoped_session.bulk_update_mappings(mapper: Mapper[Any], mappings: Iterable[Dict[str, Any]]) → None¶

Perform a bulk update of the given list of mapping dictionaries.

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

Legacy Feature

This method is a legacy feature as of the 2.0 series of SQLAlchemy. For modern bulk INSERT and UPDATE, see the sections ORM Bulk INSERT Statements and ORM Bulk UPDATE by Primary Key. The 2.0 API shares implementation details with this method and adds new features as well.

Parameters:

mapper¶ – a mapped class, or the actual Mapper object, representing the single kind of object represented within the mapping list.
mappings¶ – a sequence of dictionaries, each one containing the state of the mapped row to be updated, in terms of the attribute names on the mapped class. If the mapping refers to multiple tables, such as a joined-inheritance mapping, each dictionary may contain keys corresponding to all tables. All those keys which are present and are not part of the primary key are applied to the SET clause of the UPDATE statement; the primary key values, which are required, are applied to the WHERE clause.

Session.bulk_insert_mappings()

Session.bulk_save_objects()

method sqlalchemy.orm.scoped_session.close() → None¶

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

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

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

Tip

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

Setting the parameter Session.close_resets_only to False will instead make the close final, meaning that any further action on the session will be forbidden.

Changed in version 1.4: The Session.close() method does not immediately create a new SessionTransaction object; instead, the new SessionTransaction is created only if the Session is used again for a database operation.

See also

Closing - detail on the semantics of Session.close() and Session.reset().

Session.reset() - a similar method that behaves like close() with the parameter Session.close_resets_only set to True.

classmethod sqlalchemy.orm.scoped_session.close_all() → None¶: Close all sessions in memory.

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

Deprecated since version 1.3: The Session.close_all() method is deprecated and will be removed in a future release. Please refer to close_all_sessions().

method sqlalchemy.orm.scoped_session.commit() → None¶

Flush pending changes and commit the current transaction.

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

When the COMMIT operation is complete, all objects are fully expired, erasing their internal contents, which will be automatically re-loaded when the objects are next accessed. In the interim, these objects are in an expired state and will not function if they are detached from the Session. Additionally, this re-load operation is not supported when using asyncio-oriented APIs. The Session.expire_on_commit parameter may be used to disable this behavior.

When there is no transaction in place for the Session, indicating that no operations were invoked on this Session since the previous call to Session.commit(), the method will begin and commit an internal-only “logical” transaction, that does not normally affect the database unless pending flush changes were detected, but will still invoke event handlers and object expiration rules.

The outermost database transaction is committed unconditionally, automatically releasing any SAVEPOINTs in effect.

See also

Committing

Managing Transactions

Preventing Implicit IO when Using AsyncSession

method sqlalchemy.orm.scoped_session.configure(**kwargs: Any) → None¶

reconfigure the sessionmaker used by this scoped_session.

See sessionmaker.configure().

method sqlalchemy.orm.scoped_session.connection(bind_arguments: _BindArguments | None = None, execution_options: CoreExecuteOptionsParameter | None = None) → Connection¶

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

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

Either the Connection corresponding to the current transaction is returned, or if no transaction is in progress, a new one is begun and the Connection returned (note that no transactional state is established with the DBAPI until the first SQL statement is emitted).

Ambiguity in multi-bind or unbound Session objects can be resolved through any of the optional keyword arguments. This ultimately makes usage of the get_bind() method for resolution.

Parameters:

bind_arguments¶ – dictionary of bind arguments. May include “mapper”, “bind”, “clause”, other custom arguments that are passed to Session.get_bind().
execution_options¶ –
a dictionary of execution options that will be passed to Connection.execution_options(), when the connection is first procured only. If the connection is already present within the Session, a warning is emitted and the arguments are ignored.

See also

Setting Transaction Isolation Levels / DBAPI AUTOCOMMIT

method sqlalchemy.orm.scoped_session.delete(instance: object) → None¶

Mark an instance as deleted.

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

The object is assumed to be either persistent or detached when passed; after the method is called, the object will remain in the persistent state until the next flush proceeds. During this time, the object will also be a member of the Session.deleted collection.

When the next flush proceeds, the object will move to the deleted state, indicating a DELETE statement was emitted for its row within the current transaction. When the transaction is successfully committed, the deleted object is moved to the detached state and is no longer present within this Session.

See also

Deleting - at Basics of Using a Session

attribute sqlalchemy.orm.scoped_session.deleted¶: The set of all instances marked as ‘deleted’ within this Session

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

attribute sqlalchemy.orm.scoped_session.dirty¶

The set of all persistent instances considered dirty.

Proxied for the Session class on behalf of the scoped_session 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.orm.scoped_session.execute(statement: Executable, params: _CoreAnyExecuteParams | None = None, *, execution_options: OrmExecuteOptionsParameter = {}, bind_arguments: _BindArguments | None = None, _parent_execute_state: Any | None = None, _add_event: Any | None = None) → Result[Any]¶

Execute a SQL expression construct.

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

Returns a Result object representing results of the statement execution.

E.g.:

from sqlalchemy import select
result = session.execute(
    select(User).where(User.id == 5)
)

The API contract of Session.execute() is similar to that of Connection.execute(), the 2.0 style version of Connection.

Changed in version 1.4: the Session.execute() method is now the primary point of ORM statement execution when using 2.0 style ORM usage.

Parameters:

statement¶ – An executable statement (i.e. an Executable expression such as select()).
params¶ – Optional dictionary, or list of dictionaries, containing bound parameter values. If a single dictionary, single-row execution occurs; if a list of dictionaries, an “executemany” will be invoked. The keys in each dictionary must correspond to parameter names present in the statement.
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(), and may also provide additional options understood only in an ORM context.

See also

ORM Execution Options - ORM-specific execution options
bind_arguments¶ – dictionary of additional arguments to determine the bind. May include “mapper”, “bind”, or other custom arguments. Contents of this dictionary are passed to the Session.get_bind() method.

Returns:

a Result object.

method sqlalchemy.orm.scoped_session.expire(instance: object, attribute_names: Iterable[str] | None = None) → None¶

Expire the attributes on an instance.

Proxied for the Session class on behalf of the scoped_session 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.orm.scoped_session.expire_all() → None¶

Expires all persistent instances within this Session.

Proxied for the Session class on behalf of the scoped_session 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() is not usually needed, assuming the transaction is isolated.

See also

Refreshing / Expiring - introductory material

Session.expire()

Session.refresh()

Query.populate_existing()

method sqlalchemy.orm.scoped_session.expunge(instance: object) → None¶

Remove the instance from this Session.

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

This will free all internal references to the instance. Cascading will be applied according to the expunge cascade rule.

method sqlalchemy.orm.scoped_session.expunge_all() → None¶

Remove all object instances from this Session.

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

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

method sqlalchemy.orm.scoped_session.flush(objects: Sequence[Any] | None = None) → None¶

Flush all the object changes to the database.

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

Writes out all pending object creations, deletions and modifications to the database as INSERTs, DELETEs, UPDATEs, etc. Operations are automatically ordered by the Session’s unit of work dependency solver.

Database operations will be issued in the current transactional context and do not affect the state of the transaction, unless an error occurs, in which case the entire transaction is rolled back. You may flush() as often as you like within a transaction to move changes from Python to the database’s transaction buffer.

Parameters:

objects¶ –

Optional; restricts the flush operation to operate only on elements that are in the given collection.

This feature is for an extremely narrow set of use cases where particular objects may need to be operated upon before the full flush() occurs. It is not intended for general use.

method sqlalchemy.orm.scoped_session.get(entity: _EntityBindKey[_O], ident: _PKIdentityArgument, *, options: Sequence[ORMOption] | None = None, populate_existing: bool = False, with_for_update: ForUpdateParameter = None, identity_token: Any | None = None, execution_options: OrmExecuteOptionsParameter = {}, bind_arguments: _BindArguments | None = None) → _O | None¶

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

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

E.g.:

my_user = session.get(User, 5)

some_object = session.get(VersionedFoo, (5, 10))

some_object = session.get(
    VersionedFoo,
    {"id": 5, "version_id": 10}
)

New in version 1.4: Added Session.get(), which is moved from the now legacy Query.get() method.

Session.get() is special in that it provides direct access to the identity map of the Session. If the given primary key identifier is present in the local identity map, the object is returned directly from this collection and no SQL is emitted, unless the object has been marked fully expired. If not present, a SELECT is performed in order to locate the object.

Session.get() also will perform a check if the object is present in the identity map and marked as expired - a SELECT is emitted to refresh the object as well as to ensure that the row is still present. If not, ObjectDeletedError is raised.

Parameters:

entity¶ – a mapped class or Mapper indicating the type of entity to be loaded.
ident¶ –
A scalar, tuple, or dictionary representing the primary key. For a composite (e.g. multiple column) primary key, a tuple or dictionary should be passed.

For a single-column primary key, the scalar calling form is typically the most expedient. If the primary key of a row is the value “5”, the call looks like:
```
my_object = session.get(SomeClass, 5)
```
The tuple form contains primary key values typically in the order in which they correspond to the mapped Table object’s primary key columns, or if the Mapper.primary_key configuration parameter were used, in the order used for that parameter. For example, if the primary key of a row is represented by the integer digits “5, 10” the call would look like:
```
my_object = session.get(SomeClass, (5, 10))
```
The dictionary form should include as keys the mapped attribute names corresponding to each element of the primary key. If the mapped class has the attributes id, version_id as the attributes which store the object’s primary key value, the call would look like:
```
my_object = session.get(SomeClass, {"id": 5, "version_id": 10})
```
options¶ – optional sequence of loader options which will be applied to the query, if one is emitted.
populate_existing¶ – causes the method to unconditionally emit a SQL query and refresh the object with the newly loaded data, regardless of whether or not the object is already present.
with_for_update¶ – optional boolean True indicating FOR UPDATE should be used, or may be a dictionary containing flags to indicate a more specific set of FOR UPDATE flags for the SELECT; flags should match the parameters of Query.with_for_update(). Supersedes the Session.refresh.lockmode parameter.
execution_options¶ –
optional dictionary of execution options, which will be associated with the query execution if one is emitted. This dictionary can provide a subset of the options that are accepted by Connection.execution_options(), and may also provide additional options understood only in an ORM context.

New in version 1.4.29.

See also

ORM Execution Options - ORM-specific execution options
bind_arguments¶ –
dictionary of additional arguments to determine the bind. May include “mapper”, “bind”, or other custom arguments. Contents of this dictionary are passed to the Session.get_bind() method.

Returns:

The object instance, or None.

method sqlalchemy.orm.scoped_session.get_bind(mapper: _EntityBindKey[_O] | None = None, *, clause: ClauseElement | None = None, bind: _SessionBind | None = None, _sa_skip_events: bool | None = None, _sa_skip_for_implicit_returning: bool = False, **kw: Any) → Engine | Connection¶

Return a “bind” to which this Session is bound.

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

The “bind” is usually an instance of Engine, except in the case where the Session has been explicitly bound directly to a Connection.

For a multiply-bound or unbound Session, the mapper or clause arguments are used to determine the appropriate bind to return.

Note that the “mapper” argument is usually present when Session.get_bind() is called via an ORM operation such as a Session.query(), each individual INSERT/UPDATE/DELETE operation within a Session.flush(), call, etc.

The order of resolution is:

if mapper given and Session.binds is present, locate a bind based first on the mapper in use, then on the mapped class in use, then on any base classes that are present in the __mro__ of the mapped class, from more specific superclasses to more general.
if clause given and Session.binds is present, locate a bind based on Table objects found in the given clause present in Session.binds.
if Session.binds is present, return that.
if clause given, attempt to return a bind linked to the MetaData ultimately associated with the clause.
if mapper given, attempt to return a bind linked to the MetaData ultimately associated with the Table or other selectable to which the mapper is mapped.
No bind can be found, UnboundExecutionError is raised.

Note that the Session.get_bind() method can be overridden on a user-defined subclass of Session to provide any kind of bind resolution scheme. See the example at Custom Vertical Partitioning.

Parameters:

mapper¶ – Optional mapped class or corresponding Mapper instance. The bind can be derived from a Mapper first by consulting the “binds” map associated with this Session, and secondly by consulting the MetaData associated with the Table to which the Mapper is mapped for a bind.
clause¶ – A ClauseElement (i.e. select(), text(), etc.). If the mapper argument is not present or could not produce a bind, the given expression construct will be searched for a bound element, typically a Table associated with bound MetaData.

Session.binds

Session.bind_mapper()

Session.bind_table()

method sqlalchemy.orm.scoped_session.get_one(entity: _EntityBindKey[_O], ident: _PKIdentityArgument, *, options: Sequence[ORMOption] | None = None, populate_existing: bool = False, with_for_update: ForUpdateParameter = None, identity_token: Any | None = None, execution_options: OrmExecuteOptionsParameter = {}, bind_arguments: _BindArguments | None = None) → _O¶

Return exactly one instance based on the given primary key identifier, or raise an exception if not found.

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

Raises sqlalchemy.orm.exc.NoResultFound if the query selects no rows.

For a detailed documentation of the arguments see the method Session.get().

New in version 2.0.22.

Returns:: The object instance.

See also

Session.get() - equivalent method that instead: returns None if no row was found with the provided primary key

Return an identity key.

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

This is an alias of identity_key().

attribute sqlalchemy.orm.scoped_session.identity_map¶: Proxy for the Session.identity_map attribute on behalf of the scoped_session class.

attribute sqlalchemy.orm.scoped_session.info¶

A user-modifiable dictionary.

Proxied for the Session class on behalf of the scoped_session 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.

attribute sqlalchemy.orm.scoped_session.is_active¶

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

Proxied for the Session class on behalf of the scoped_session 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.

Session.in_transaction()

method sqlalchemy.orm.scoped_session.is_modified(instance: object, include_collections: bool = True) → bool¶

Return True if the given instance has locally modified attributes.

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

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

It is in effect a more expensive and accurate version of checking for the given instance in the Session.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.orm.scoped_session.merge(instance: _O, *, load: bool = True, options: Sequence[ORMOption] | None = None) → _O¶

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

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

Session.merge() examines the primary key attributes of the source instance, and attempts to reconcile it with an instance of the same primary key in the session. If not found locally, it attempts to load the object from the database based on primary key, and if none can be located, creates a new instance. The state of each attribute on the source instance is then copied to the target instance. The resulting target instance is then returned by the method; the original source instance is left unmodified, and un-associated with the Session if not already.

This operation cascades to associated instances if the association is mapped with cascade="merge".

See Merging for a detailed discussion of merging.

Parameters:

instance¶ – Instance to be merged.
load¶ –
Boolean, when False, merge() switches into a “high performance” mode which causes it to forego emitting history events as well as all database access. This flag is used for cases such as transferring graphs of objects into a Session from a second level cache, or to transfer just-loaded objects into the Session owned by a worker thread or process without re-querying the database.

The load=False use case adds the caveat that the given object has to be in a “clean” state, that is, has no pending changes to be flushed - even if the incoming object is detached from any Session. This is so that when the merge operation populates local attributes and cascades to related objects and collections, the values can be “stamped” onto the target object as is, without generating any history or attribute events, and without the need to reconcile the incoming data with any existing related objects or collections that might not be loaded. The resulting objects from load=False are always produced as “clean”, so it is only appropriate that the given objects should be “clean” as well, else this suggests a mis-use of the method.
options¶ –
optional sequence of loader options which will be applied to the Session.get() method when the merge operation loads the existing version of the object from the database.

New in version 1.4.24.

See also

make_transient_to_detached() - provides for an alternative means of “merging” a single object into the Session

attribute sqlalchemy.orm.scoped_session.new¶: The set of all instances marked as ‘new’ within this Session.

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

attribute sqlalchemy.orm.scoped_session.no_autoflush¶

Return a context manager that disables autoflush.

Proxied for the Session class on behalf of the scoped_session 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.orm.scoped_session.object_session(instance: object) → Session | None¶

Return the Session to which an object belongs.

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

This is an alias of object_session().

method sqlalchemy.orm.scoped_session.query(*entities: _ColumnsClauseArgument[Any], **kwargs: Any) → Query[Any]¶

Return a new Query object corresponding to this Session.

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

Note that the Query object is legacy as of SQLAlchemy 2.0; the select() construct is now used to construct ORM queries.

See also

SQLAlchemy Unified Tutorial

ORM Querying Guide

Legacy Query API - legacy API doc

method sqlalchemy.orm.scoped_session.query_property(query_cls: Type[Query[_T]] | None = None) → QueryPropertyDescriptor¶

return a class property which produces a legacy Query object against the class and the current Session when called.

Legacy Feature

The scoped_session.query_property() accessor is specific to the legacy Query object and is not considered to be part of 2.0-style ORM use.

e.g.:

from sqlalchemy.orm import QueryPropertyDescriptor
from sqlalchemy.orm import scoped_session
from sqlalchemy.orm import sessionmaker

Session = scoped_session(sessionmaker())

class MyClass:
    query: QueryPropertyDescriptor = Session.query_property()

# after mappers are defined
result = MyClass.query.filter(MyClass.name=='foo').all()

Produces instances of the session’s configured query class by default. To override and use a custom implementation, provide a query_cls callable. The callable will be invoked with the class’s mapper as a positional argument and a session keyword argument.

There is no limit to the number of query properties placed on a class.

method sqlalchemy.orm.scoped_session.refresh(instance: object, attribute_names: Iterable[str] | None = None, with_for_update: ForUpdateParameter = None) → None¶

Expire and refresh attributes on the given instance.

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

The selected attributes will first be expired as they would when using Session.expire(); then a SELECT statement will be issued to the database to refresh column-oriented attributes with the current value available in the current transaction.

relationship() oriented attributes will also be immediately loaded if they were already eagerly loaded on the object, using the same eager loading strategy that they were loaded with originally.

New in version 1.4: - the Session.refresh() method can also refresh eagerly loaded attributes.

relationship() oriented attributes that would normally load using the select (or “lazy”) loader strategy will also load if they are named explicitly in the attribute_names collection, emitting a SELECT statement for the attribute using the immediate loader strategy. If lazy-loaded relationships are not named in Session.refresh.attribute_names, then they remain as “lazy loaded” attributes and are not implicitly refreshed.

Changed in version 2.0.4: The Session.refresh() method will now refresh lazy-loaded relationship() oriented attributes for those which are named explicitly in the Session.refresh.attribute_names collection.

Tip

While the Session.refresh() method is capable of refreshing both column and relationship oriented attributes, its primary focus is on refreshing of local column-oriented attributes on a single instance. For more open ended “refresh” functionality, including the ability to refresh the attributes on many objects at once while having explicit control over relationship loader strategies, use the populate existing feature instead.

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. Refreshing attributes usually only makes sense at the start of a transaction where database rows have not yet been accessed.

Parameters:

attribute_names¶ – optional. An iterable collection of string attribute names indicating a subset of attributes to be refreshed.
with_for_update¶ – optional boolean True indicating FOR UPDATE should be used, or may be a dictionary containing flags to indicate a more specific set of FOR UPDATE flags for the SELECT; flags should match the parameters of Query.with_for_update(). Supersedes the Session.refresh.lockmode parameter.

See also

Refreshing / Expiring - introductory material

Session.expire()

Session.expire_all()

Populate Existing - allows any ORM query to refresh objects as they would be loaded normally.

method sqlalchemy.orm.scoped_session.remove() → None¶

Dispose of the current Session, if present.

This will first call Session.close() method on the current Session, which releases any existing transactional/connection resources still being held; transactions specifically are rolled back. The Session is then discarded. Upon next usage within the same scope, the scoped_session will produce a new Session object.

method sqlalchemy.orm.scoped_session.reset() → None¶

Close out the transactional resources and ORM objects used by this Session, resetting the session to its initial state.

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

This method provides for same “reset-only” behavior that the Session.close() method has provided historically, where the state of the Session is reset as though the object were brand new, and ready to be used again. This method may then be useful for Session objects which set Session.close_resets_only to False, so that “reset only” behavior is still available.

New in version 2.0.22.

See also

Closing - detail on the semantics of Session.close() and Session.reset().

Session.close() - a similar method will additionally prevent re-use of the Session when the parameter Session.close_resets_only is set to False.

method sqlalchemy.orm.scoped_session.rollback() → None¶

Rollback the current transaction in progress.

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

If no transaction is in progress, this method is a pass-through.

The method always rolls back the topmost database transaction, discarding any nested transactions that may be in progress.

See also

Rolling Back

Managing Transactions

method sqlalchemy.orm.scoped_session.scalar(statement: Executable, params: _CoreSingleExecuteParams | None = None, *, execution_options: OrmExecuteOptionsParameter = {}, bind_arguments: _BindArguments | None = None, **kw: Any) → Any¶

Execute a statement and return a scalar result.

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

Usage and parameters are the same as that of Session.execute(); the return result is a scalar Python value.

method sqlalchemy.orm.scoped_session.scalars(statement: Executable, params: _CoreAnyExecuteParams | None = None, *, execution_options: OrmExecuteOptionsParameter = {}, bind_arguments: _BindArguments | None = None, **kw: Any) → ScalarResult[Any]¶

Execute a statement and return the results as scalars.

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

Usage and parameters are the same as that of Session.execute(); the return result is a ScalarResult filtering object which will return single elements rather than Row objects.

Returns:: a ScalarResult object

New in version 1.4.24: Added Session.scalars()

New in version 1.4.26: Added scoped_session.scalars()

See also

Selecting ORM Entities - contrasts the behavior of Session.execute() to Session.scalars()

attribute sqlalchemy.orm.scoped_session.session_factory: sessionmaker[_S]¶: The session_factory provided to __init__ is stored in this attribute and may be accessed at a later time. This can be useful when a new non-scoped Session is needed.

class sqlalchemy.util.ScopedRegistry¶

A Registry that can store one or multiple instances of a single class on the basis of a “scope” function.

The object implements __call__ as the “getter”, so by calling myregistry() the contained object is returned for the current scope.

Parameters:

createfunc¶ – a callable that returns a new object to be placed in the registry
scopefunc¶ – a callable that will return a key to store/retrieve an object.

Members

__init__(), clear(), has(), set()

Class signature

class sqlalchemy.util.ScopedRegistry (typing.Generic)

method sqlalchemy.util.ScopedRegistry.__init__(createfunc: Callable[[], _T], scopefunc: Callable[[], Any])¶

Construct a new ScopedRegistry.

Parameters:

createfunc¶ – A creation function that will generate a new value for the current scope, if none is present.
scopefunc¶ – A function that returns a hashable token representing the current scope (such as, current thread identifier).

method sqlalchemy.util.ScopedRegistry.clear() → None¶: Clear the current scope, if any.

method sqlalchemy.util.ScopedRegistry.has() → bool¶: Return True if an object is present in the current scope.

method sqlalchemy.util.ScopedRegistry.set(obj: _T) → None¶: Set the value for the current scope.

class sqlalchemy.util.ThreadLocalRegistry¶: A ScopedRegistry that uses a threading.local() variable for storage.

Class signature

class sqlalchemy.util.ThreadLocalRegistry (sqlalchemy.util.ScopedRegistry)

class sqlalchemy.orm.QueryPropertyDescriptor¶: Describes the type applied to a class-level scoped_session.query_property() attribute.

New in version 2.0.5.

Class signature

class sqlalchemy.orm.QueryPropertyDescriptor (typing_extensions.Protocol)

SQLAlchemy 2.0 Documentation - 私家版日本語訳ドキュメント

SQLAlchemy 2.0 Documentation - 私家版日本語訳ドキュメント

SQLAlchemy ORM

Contextual/Thread-local Sessions¶

Implicit Method Access¶

Thread-Local Scope¶

Using Thread-Local Scope with Web Applications¶

Using Custom Created Scopes¶

Contextual Session API¶