DatabaseSessionDependency

class safir.dependencies.db_session.DatabaseSessionDependency

Bases: object

Manages an async per-request SQLAlchemy session.

Notes

Creation of the database session factory has to be deferred until the configuration has been loaded, which in turn is deferred until app startup.

In the app startup hook, run:

await db_session_dependency.initialize(database_url)

In the app shutdown hook, run:

await db_session_dependency.aclose()

An isolation level may optionally be configured when calling initialize. By default, a transaction is opened for every request and committed at the end of that request. This can be configured when calling initialize.

Methods Summary

__call__()	Create a database session and open a transaction.
aclose()	Shut down the database engine.
initialize(url, password, *[, ...])	Initialize the session dependency.

Methods Documentation

async __call__() → AsyncIterator[sqlalchemy.ext.asyncio.scoping.async_scoped_session]

Create a database session and open a transaction.

By default, this implements a policy of one request equals one transaction, which is closed when that request returns. To disable managed transactions, pass manage_transactions=False to the initialize method.

Returns

session – The newly-created session.

Return type

sqlalchemy.ext.asyncio.AsyncSession

async aclose() → None

Shut down the database engine.

async initialize(url: str, password: Optional[str], *, isolation_level: Optional[str] = None, manage_transactions: bool = True) → None

Initialize the session dependency.

Parameters

• url (str) – Database connection URL, not including the password.

• password (str or None) – Database connection password.

• isolation_level (str, optional) – If specified, sets a non-default isolation level for the database engine.

• manage_transactions (bool, optional) – Whether the dependency should open a new transaction for each request and commit that transaction at the end of the request. This is the default behavior; to manage transactions manually, set this parameter to False. (Disabling managed transactions may be necessary if the application database code has to retry failed transactions due to a non-default isolation level.)