locking.rst

Locking

Explicit table-level locks are supported through the psqlextra.locking.postgres_lock_model and psqlextra.locking.postgres_lock_table methods. All table-level lock methods are supported.

Locks are always bound to the current transaction and are released when the transaction is committed or rolled back. There is no support (in PostgreSQL) for explicitly releasing a lock.

Warning

Locks are only released when the outer transaction commits or when a nested transaction is rolled back. You can ensure that the transaction you created is the outermost one by passing the durable=True argument to transaction.atomic.

Note

Use django-pglocks if you need a advisory lock.

Locking a model

Use psqlextra.locking.PostgresTableLockMode to indicate the type of lock to acquire.

from django.db import transaction

from psqlextra.locking import PostgresTableLockMode, postgres_lock_table

with transaction.atomic(durable=True):
    postgres_lock_model(MyModel, PostgresTableLockMode.EXCLUSIVE)

# locks are released here, when the transaction committed

Locking a table

Use psqlextra.locking.postgres_lock_table to lock arbitrary tables in arbitrary schemas.

from django.db import transaction

from psqlextra.locking import PostgresTableLockMode, postgres_lock_table

with transaction.atomic(durable=True):
    postgres_lock_table("mytable", PostgresTableLockMode.EXCLUSIVE)
    postgres_lock_table(
        "tableinotherschema",
        PostgresTableLockMode.EXCLUSIVE,
        schema_name="myschema"
    )

# locks are released here, when the transaction committed