index.community/scraper/management/commands/_util.py
2018-08-27 00:12:24 +02:00

40 lines
1 KiB
Python

LOCK_MODES = (
'ACCESS SHARE',
'ROW SHARE',
'ROW EXCLUSIVE',
'SHARE UPDATE EXCLUSIVE',
'SHARE',
'SHARE ROW EXCLUSIVE',
'EXCLUSIVE',
'ACCESS EXCLUSIVE',
)
def require_lock(model, lock):
"""
Decorator for PostgreSQL's table-level lock functionality
Example:
@transaction.commit_on_success
@require_lock(MyModel, 'ACCESS EXCLUSIVE')
def myview(request)
...
PostgreSQL's LOCK Documentation:
http://www.postgresql.org/docs/8.3/interactive/sql-lock.html
"""
def require_lock_decorator(view_func):
def wrapper(*args, **kwargs):
if lock not in LOCK_MODES:
raise ValueError('%s is not a PostgreSQL supported lock mode.')
from django.db import connection
cursor = connection.cursor()
cursor.execute(
'LOCK TABLE %s IN %s MODE' % (model._meta.db_table, lock)
)
return view_func(*args, **kwargs)
return wrapper
return require_lock_decorator