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Fixed comments related to nonexistent keys for incr()/decr() in memcached backends.

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Nick Pope 2020-08-14 22:58:16 +01:00 committed by Mariusz Felisiak
parent 67e4a9a4b9
commit 0cb0d59b23
1 changed files with 8 additions and 12 deletions
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20
django/core/cache/backends/memcached.py vendored
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@ -18,10 +18,8 @@ class BaseMemcachedCache(BaseCache):
else:
self._servers = server
# The exception type to catch from the underlying library for a key
# that was not found. This is a ValueError for python-memcache,
# pylibmc.NotFound for pylibmc, and cmemcache will return None without
# raising an exception.
# Exception type raised by the underlying client library for a
# nonexistent key.
self.LibraryValueNotFoundException = value_not_found_exception
self._lib = library
@ -106,10 +104,8 @@ class BaseMemcachedCache(BaseCache):
try:
val = self._cache.incr(key, delta)
# python-memcache responds to incr on nonexistent keys by
# raising a ValueError, pylibmc by raising a pylibmc.NotFound
# and Cmemcache returns None. In all cases,
# we should raise a ValueError though.
# Normalize an exception raised by the underlying client library to
# ValueError in the event of a nonexistent key when calling incr().
except self.LibraryValueNotFoundException:
val = None
if val is None:
@ -125,10 +121,8 @@ class BaseMemcachedCache(BaseCache):
try:
val = self._cache.decr(key, delta)
# python-memcache responds to incr on nonexistent keys by
# raising a ValueError, pylibmc by raising a pylibmc.NotFound
# and Cmemcache returns None. In all cases,
# we should raise a ValueError though.
# Normalize an exception raised by the underlying client library to
# ValueError in the event of a nonexistent key when calling decr().
except self.LibraryValueNotFoundException:
val = None
if val is None:
@ -160,6 +154,8 @@ class BaseMemcachedCache(BaseCache):
class MemcachedCache(BaseMemcachedCache):
"An implementation of a cache binding using python-memcached"
def __init__(self, server, params):
# python-memcached ≥ 1.45 returns None for a nonexistent key in
# incr/decr(), python-memcached < 1.45 raises ValueError.
import memcache
super().__init__(server, params, library=memcache, value_not_found_exception=ValueError)