Question

I’m caching views in my Django project.

@cache_page(60 * 15)
def view_to_cache

Because users can edit the content, I’d like to delete specific caches when a user makes an edit. To do this, I’ll cache.delete(KEY) at the end of the edit function.

The problem is, I’m not sure how to get the value of the appropriate key to delete.

I ran memcached_stats to get the keys, and they’re all random. Any idea how I’d know what key to delete? Here’s a sample of the cache:

>>> from memcached_stats import MemcachedStats
>>> mem = MemcachedStats()
>>> mem.stats()
{'auth_cmds': '0', 'reclaimed': '0', 'pid': '67140', 'cas_hits': '0', 'uptime': '3075', 'delete_misses': '0', 'listen_disabled_num': '0', 'cas_misses': '0', 'decr_hits': '0', 'incr_hits': '0', 'version': '1.4.5', 'limit_maxbytes': '67108864', 'bytes_written': '13604', 'incr_misses': '0', 'accepting_conns': '1', 'rusage_system': '0.073969', 'total_items': '13', 'cmd_get': '26', 'curr_connections': '12', 'threads': '4', 'total_connections': '33', 'cmd_set': '13', 'curr_items': '9', 'conn_yields': '0', 'get_misses': '7', 'bytes_read': '24226', 'cas_badval': '0', 'cmd_flush': '0', 'evictions': '0', 'bytes': '19492', 'connection_structures': '14', 'auth_errors': '0', 'rusage_user': '0.063413', 'time': '1327784334', 'delete_hits': '1', 'pointer_size': '64', 'decr_misses': '0', 'get_hits': '19'}
>>> mem.keys()
[':1:django.contrib.sessions.cachec7a594602214b4992c53575b3eda010d', ':1:views.decorators.cache.cache_header..511894add8326666c1a436bdb37e50ce.en-us', ':1:views.decorators.cache.cache_header..642ae686efc6dbc27b334fc0e1d22641.en-us', ':1:views.decorators.cache.cache_header..7739f0feb4375839a76f5cae2d10a69c.en-us', ':1:views.decorators.cache.cache_header..e32e41ea17bca494f9794fa87f5ec0d6.en-us', ':1:views.decorators.cache.cache_page..GET.511894add8326666c1a436bdb37e50ce.d41d8cd98f00b204e9800998ecf8427e.en-us', ':1:views.decorators.cache.cache_page..GET.642ae686efc6dbc27b334fc0e1d22641.d41d8cd98f00b204e9800998ecf8427e.en-us', ':1:views.decorators.cache.cache_page..GET.7739f0feb4375839a76f5cae2d10a69c.d41d8cd98f00b204e9800998ecf8427e.en-us', ':1:views.decorators.cache.cache_page..GET.e32e41ea17bca494f9794fa87f5ec0d6.d41d8cd98f00b204e9800998ecf8427e.en-us']
>>> cache.has_key(':1:django.contrib.sessions.cachec7a594602214b4992c53575b3eda010d')
Traceback (most recent call last):
  File "<console>", line 1, in <module>
NameError: name 'cache' is not defined
>>> from django.core.cache import cache
>>> cache.has_key(':1:django.contrib.sessions.cachec7a594602214b4992c53575b3eda010d')
False
>>> cache.has_key('1:django.contrib.sessions.cachec7a594602214b4992c53575b3eda010d')
False
>>> cache.has_key('django.contrib.sessions.cachec7a594602214b4992c53575b3eda010d')
True
>>> cache.has_key('views.decorators.cache.cache_page..GET.e32e41ea17bca494f9794fa87f5ec0d6.d41d8cd98f00b204e9800998ecf8427e.en-us')

Answer 1

They are not random, they are md5 hashes of the URL. There is a get_cache_key in django.utils.cache which can use or look at to recreate the keys. It accepts a request object and I think it uses request.path and settings.LANGUAGE_CODE.