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Code Issues 24 Releases Wiki Activity

Fixed #11569 -- Wrapped DatabaseCache._base_set in an atomic block. 

The atomic block provides a clean rollback to a savepoint on failed writes.

The ticket reported a race condition which I don't know how to test.
This commit is contained in:
Aymeric Augustin 2013-03-11 22:16:37 +01:00
parent faabf3614e
commit 1b12e248ea
1 changed files with 15 additions and 14 deletions
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29
django/core/cache/backends/db.py vendored
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@ -10,7 +10,7 @@ except ImportError:
from django.conf import settings
from django.core.cache.backends.base import BaseCache
from django.db import connections, router, DatabaseError
from django.db import connections, transaction, router, DatabaseError
from django.utils import timezone, six
from django.utils.encoding import force_bytes
@ -26,7 +26,7 @@ class Options(object):
self.model_name = 'cacheentry'
self.verbose_name = 'cache entry'
self.verbose_name_plural = 'cache entries'
self.object_name = 'CacheEntry'
self.object_name = 'CacheEntry'
self.abstract = False
self.managed = True
self.proxy = False
@ -108,19 +108,20 @@ class DatabaseCache(BaseDatabaseCache):
# string, not bytes. Refs #19274.
if six.PY3:
b64encoded = b64encoded.decode('latin1')
cursor.execute("SELECT cache_key, expires FROM %s "
"WHERE cache_key = %%s" % table, [key])
try:
result = cursor.fetchone()
if result and (mode == 'set' or
(mode == 'add' and result[1] < now)):
cursor.execute("UPDATE %s SET value = %%s, expires = %%s "
"WHERE cache_key = %%s" % table,
[b64encoded, connections[db].ops.value_to_db_datetime(exp), key])
else:
cursor.execute("INSERT INTO %s (cache_key, value, expires) "
"VALUES (%%s, %%s, %%s)" % table,
[key, b64encoded, connections[db].ops.value_to_db_datetime(exp)])
with transaction.atomic_if_autocommit(using=db):
cursor.execute("SELECT cache_key, expires FROM %s "
"WHERE cache_key = %%s" % table, [key])
result = cursor.fetchone()
exp = connections[db].ops.value_to_db_datetime(exp)
if result and (mode == 'set' or (mode == 'add' and result[1] < now)):
cursor.execute("UPDATE %s SET value = %%s, expires = %%s "
"WHERE cache_key = %%s" % table,
[b64encoded, exp, key])
else:
cursor.execute("INSERT INTO %s (cache_key, value, expires) "
"VALUES (%%s, %%s, %%s)" % table,
[key, b64encoded, exp])
except DatabaseError:
# To be threadsafe, updates/inserts are allowed to fail silently
return False