Transactions

Peewee-async provides several interfaces similiar to peewee for working with transactions.

The most general interface are aio_atomic() and aio_transaction() methods which work as context managers. The aio_atomic() method supports nested transactions and run the block of code in a transaction or savepoint, depending on the level of nesting. If an exception occurs in a wrapped block, the current transaction/savepoint will be rolled back. Otherwise the statements will be committed at the end of the wrapped block.

async with db.aio_atomic(): # BEGIN
    await TestModel.aio_create(text='FOO') # INSERT INTO "testmodel" ("text", "data") VALUES ('FOO', '') RETURNING "testmodel"."id"

    async with db.aio_atomic(): # SAVEPOINT PWASYNC__e83bf5fc118f4e28b0fbdac90ab857ca
        await TestModel.update(text="BAR").aio_execute() # UPDATE "testmodel" SET "text" = 'BAR'
    # RELEASE SAVEPOINT PWASYNC__e83bf5fc118f4e28b0fbdac90ab857ca
# COMMIT

The aio_transcation() method does not allow nested transactions and run the block of code in a transaction.

async with db.aio_atomic(): # BEGIN
    await TestModel.aio_create(text='FOO') # INSERT INTO "testmodel" ("text", "data") VALUES ('FOO', '') RETURNING "testmodel"."id"
# COMMIT

Using nested aio_transcation() will lead to OperationalError.

Manual management

If you want to manage transactions manually you have to acquire a connection by yourself and manage the transaction inside the context manager of the connection:

from peewee_async import Transaction
async with db.aio_connection() as connection:
    tr = Transaction(connection)
    await tr.begin() # BEGIN
    await TestModel.aio_create(text='FOO')
    try:
        await TestModel.aio_create(text='FOO')
    except:
        await tr.rollback() # ROLLBACK
    else:
        await tr.commit() # COMMIT

Raw sql for transactions

if the above options are not enough for you you can always use raw sql for more opportunities:

async with db.aio_connection() as connection:
    await db.aio_execute_sql(sql="begin isolation level repeatable read;")
    await TestModel.aio_create(text='FOO')
    try:
        await TestModel.aio_create(text='FOO')
    except:
        await await db.aio_execute_sql(sql="ROLLBACK")
    else:
        await await db.aio_execute_sql(sql="COMMIT")

Just remember a transaction should work during one connection.

Aware different tasks when working with transactions.

As has been said a transaction should work during one connection. And as you know from the connection section every connection is got from the contextvar variable which means every asyncio.Task has an own connection. So this example will not work and may lead to bugs:

async with db.aio_atomic():
    await asyncio.gather(TestModel.aio_create(text='FOO1'), TestModel.aio_create(text='FOO2'), TestModel.aio_create(text='FOO3'))

Every sql query of the exmaple will run in the separate task which know nothing about started transaction in main task.