Hi Erik,
If you want a nicer interface, I just ran manage.py inspecdb on one of my
databases and got this for the cache table. Not sure why django still does
it by hand.
class Cache(models.Model):
cache_key = models.CharField(primary_key=True, max_length=255)
value = models.TextField()
expires = models.DateTimeField()
class Meta:
managed = False
db_table = 'cache_table'
Collin
On Friday, December 19, 2014 8:03:39 AM UTC-5, Erik Cederstrand wrote:
>
>
> > Den 18/12/2014 kl. 12.20 skrev Erik Cederstrand <[email protected]
> <javascript:>>:
> >
> > Hi list,
> >
> > I'm using Django as a hub to synchronize data between various external
> systems. To do this, I have some long-running Django management commands
> that are started as cron jobs. To ensure that only one job is working on a
> data set at any one time, I have implemented a locking system using the
> Django cache system.
> >
> > Due to my less-than-stellar programming talent, a cron job may need to
> be killed once in a while. To avoid leaving orphaned locks in the cache, I
> want to clean up any locks before exiting, and I may not know which cache
> keys exist at the time of exit. Therefore, I want to write a signal handler
> that searches the Django cache for any entries that can be traced to the
> current process (my cache keys can be used for this purpose) and delete
> those.
> >
> > AFAICS, the Django cache API can't be used for this. There's
> cache.clear() but I don't want to delete all cache entries. I'm using the
> database backend, so I'm thinking I could access the database table
> directly and issue any custom SQL on that. But it does feel hackish, so
> maybe one of you have a better approach? Maybe I got the whole thing
> backwards?
>
> Just to wrap this up, I wrote a function to get all or some cache entries.
> Most of the code is copy-paste from django.core.cache.backends.db.
>
>
> def get_cache_entries(key_prefix=None):
> db = router.db_for_read(cache.cache_model_class)
> table = connections[db].ops.quote_name(cache._table)
> with connections[db].cursor() as cursor:
> sql = "SELECT cache_key, value FROM %s" % table
> params = None
> if key_prefix:
> sql += " WHERE cache_key LIKE %s"
> params = (key_prefix + '%',)
> cursor.execute(sql, params=params)
> rows = cursor.fetchall()
> res = {}
> for row in rows:
> value = connections[db].ops.process_clob(row[1])
> res[row[0]] = pickle.loads(base64.b64decode(force_bytes(value)))
> return res
>
>
> Erik
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