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