Commit 1b12e248 authored by Aymeric Augustin's avatar Aymeric Augustin
Browse files

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.
parent faabf361

django/core/cache/backends/db.py

+15 −14
Original line number Diff line number Diff line
@@ -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
@@ -108,19 +108,20 @@ class DatabaseCache(BaseDatabaseCache): 
        # string, not bytes. Refs #19274.

        if six.PY3:

            b64encoded = b64encoded.decode('latin1')

        try:

            with transaction.atomic_if_autocommit(using=db):

                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)):

                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, connections[db].ops.value_to_db_datetime(exp), key])

                                   [b64encoded, 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)])

                                   [key, b64encoded, exp])

        except DatabaseError:

            # To be threadsafe, updates/inserts are allowed to fail silently

            return False