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Refactored datetime handling in the database cache backend. 

Took advantage of the new database adapters and converters.
This commit is contained in:
Aymeric Augustin 2015-05-02 22:25:57 +02:00
parent 2a05a82311
commit e2a652fac1
1 changed files with 43 additions and 43 deletions
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86
django/core/cache/backends/db.py vendored
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@ -4,8 +4,7 @@ from datetime import datetime
from django.conf import settings
from django.core.cache.backends.base import DEFAULT_TIMEOUT, BaseCache
from django.db import DatabaseError, connections, router, transaction
from django.db.backends.utils import typecast_timestamp
from django.db import DatabaseError, connections, models, router, transaction
from django.utils import six, timezone
from django.utils.encoding import force_bytes
@ -46,43 +45,40 @@ class BaseDatabaseCache(BaseCache):
class DatabaseCache(BaseDatabaseCache):
# This class uses cursors provided by the database connection. This means
# it reads expiration values as aware or naive datetimes depending on the
# value of USE_TZ. They must be compared to aware or naive representations
# of "now" respectively.
# But it bypasses the ORM for write operations. As a consequence, aware
# datetimes aren't made naive for databases that don't support time zones.
# We work around this problem by always using naive datetimes when writing
# expiration values, in UTC when USE_TZ = True and in local time otherwise.
# it reads expiration values as aware or naive datetimes, depending on the
# value of USE_TZ and whether the database supports time zones. The ORM's
# conversion and adaptation infrastructure is then used to avoid comparing
# aware and naive datetimes accidentally.
def get(self, key, default=None, version=None):
key = self.make_key(key, version=version)
self.validate_key(key)
db = router.db_for_read(self.cache_model_class)
table = connections[db].ops.quote_name(self._table)
connection = connections[db]
table = connection.ops.quote_name(self._table)
with connections[db].cursor() as cursor:
with connection.cursor() as cursor:
cursor.execute("SELECT cache_key, value, expires FROM %s "
"WHERE cache_key = %%s" % table, [key])
row = cursor.fetchone()
if row is None:
return default
now = timezone.now()
expires = row[2]
if connections[db].features.needs_datetime_string_cast and not isinstance(expires, datetime):
# Note: typecasting is needed by some 3rd party database backends.
# All core backends work without typecasting, so be careful about
# changes here - test suite will NOT pick regressions here.
expires = typecast_timestamp(str(expires))
if settings.USE_TZ:
expires = expires.replace(tzinfo=timezone.utc)
if expires < now:
expression = models.Expression(output_field=models.DateTimeField())
for converter in (connection.ops.get_db_converters(expression) +
expression.get_db_converters(connection)):
expires = converter(expires, expression, connection, {})
if expires < timezone.now():
db = router.db_for_write(self.cache_model_class)
with connections[db].cursor() as cursor:
connection = connections[db]
with connection.cursor() as cursor:
cursor.execute("DELETE FROM %s "
"WHERE cache_key = %%s" % table, [key])
return default
value = connections[db].ops.process_clob(row[1])
value = connection.ops.process_clob(row[1])
return pickle.loads(base64.b64decode(force_bytes(value)))
def set(self, key, value, timeout=DEFAULT_TIMEOUT, version=None):
@ -98,9 +94,10 @@ class DatabaseCache(BaseDatabaseCache):
def _base_set(self, mode, key, value, timeout=DEFAULT_TIMEOUT):
timeout = self.get_backend_timeout(timeout)
db = router.db_for_write(self.cache_model_class)
table = connections[db].ops.quote_name(self._table)
connection = connections[db]
table = connection.ops.quote_name(self._table)
with connections[db].cursor() as cursor:
with connection.cursor() as cursor:
cursor.execute("SELECT COUNT(*) FROM %s" % table)
num = cursor.fetchone()[0]
now = timezone.now()
@ -129,14 +126,15 @@ class DatabaseCache(BaseDatabaseCache):
cursor.execute("SELECT cache_key, expires FROM %s "
"WHERE cache_key = %%s" % table, [key])
result = cursor.fetchone()
if result:
current_expires = result[1]
if (connections[db].features.needs_datetime_string_cast and not
isinstance(current_expires, datetime)):
current_expires = typecast_timestamp(str(current_expires))
if settings.USE_TZ:
current_expires = current_expires.replace(tzinfo=timezone.utc)
exp = connections[db].ops.adapt_datetimefield_value(exp)
expression = models.Expression(output_field=models.DateTimeField())
for converter in (connection.ops.get_db_converters(expression) +
expression.get_db_converters(connection)):
current_expires = converter(current_expires, expression, connection, {})
exp = connection.ops.adapt_datetimefield_value(exp)
if result and (mode == 'set' or (mode == 'add' and current_expires < now)):
cursor.execute("UPDATE %s SET value = %%s, expires = %%s "
"WHERE cache_key = %%s" % table,
@ -156,9 +154,10 @@ class DatabaseCache(BaseDatabaseCache):
self.validate_key(key)
db = router.db_for_write(self.cache_model_class)
table = connections[db].ops.quote_name(self._table)
connection = connections[db]
table = connection.ops.quote_name(self._table)
with connections[db].cursor() as cursor:
with connection.cursor() as cursor:
cursor.execute("DELETE FROM %s WHERE cache_key = %%s" % table, [key])
def has_key(self, key, version=None):
@ -166,7 +165,8 @@ class DatabaseCache(BaseDatabaseCache):
self.validate_key(key)
db = router.db_for_read(self.cache_model_class)
table = connections[db].ops.quote_name(self._table)
connection = connections[db]
table = connection.ops.quote_name(self._table)
if settings.USE_TZ:
now = datetime.utcnow()
@ -174,27 +174,26 @@ class DatabaseCache(BaseDatabaseCache):
now = datetime.now()
now = now.replace(microsecond=0)
with connections[db].cursor() as cursor:
with connection.cursor() as cursor:
cursor.execute("SELECT cache_key FROM %s "
"WHERE cache_key = %%s and expires > %%s" % table,
[key, connections[db].ops.adapt_datetimefield_value(now)])
[key, connection.ops.adapt_datetimefield_value(now)])
return cursor.fetchone() is not None
def _cull(self, db, cursor, now):
if self._cull_frequency == 0:
self.clear()
else:
# When USE_TZ is True, 'now' will be an aware datetime in UTC.
now = now.replace(tzinfo=None)
table = connections[db].ops.quote_name(self._table)
connection = connections[db]
table = connection.ops.quote_name(self._table)
cursor.execute("DELETE FROM %s WHERE expires < %%s" % table,
[connections[db].ops.adapt_datetimefield_value(now)])
[connection.ops.adapt_datetimefield_value(now)])
cursor.execute("SELECT COUNT(*) FROM %s" % table)
num = cursor.fetchone()[0]
if num > self._max_entries:
cull_num = num // self._cull_frequency
cursor.execute(
connections[db].ops.cache_key_culling_sql() % table,
connection.ops.cache_key_culling_sql() % table,
[cull_num])
cursor.execute("DELETE FROM %s "
"WHERE cache_key < %%s" % table,
@ -202,6 +201,7 @@ class DatabaseCache(BaseDatabaseCache):
def clear(self):
db = router.db_for_write(self.cache_model_class)
table = connections[db].ops.quote_name(self._table)
with connections[db].cursor() as cursor:
connection = connections[db]
table = connection.ops.quote_name(self._table)
with connection.cursor() as cursor:
cursor.execute('DELETE FROM %s' % table)