def advisory_lock_by_relation_name(self, cursor, rel_name: str):
"""
Try acquiring a PG advisory lock by an integer identifier matching the specified relation name and exit
immediately.
This is equal locking by table name until the transaction ends.
:param cursor:
:param rel_name:
:return:
"""
sql = SQLClause('''select pg_try_advisory_xact_lock(
(select c.oid id from pg_class c where c.relname = %s limit 1)::integer
)''', [rel_name])
return fetch_bool(cursor, sql)
def _send_digest_scheduled(run_date: datetime) -> bool:
with connection.cursor() as cursor:
sql = '''select exists(select id from task_task
where name = %s and (kwargs->>'run_date')::timestamptz = %s)'''
return fetch_bool(cursor, SQLClause(sql, [SendDigest.name, run_date]))