[support] When are Caches Cleared?

[Earnie Boyd]

Fred Jones wrote:
>>> Question is when does it expire? I see there is a minimum and mine is
>>> set to NONE. I *think* what I am asking is about the maximum.
>>
>> That would depend on the "cache_flush_$table" variable and the
>> cache_lifetime variable and whether or not the cache is deemed
>> CACHE_PERMANENT (a.k.a. expire == 0).  See
>> http://api.drupal.org/api/function/cache_get/6 for more information.
>> CACHE_PERMANENT should only be used for things like variables data and
>> the theme_registry.  'cache_lifetime' is the variable for the minimum.
>>
>> Tracing through it, maybe there is a bug but I don't know it to be.  I
>> am sure that if "cache_flush_$table" isn't set that the cache will never
>> be deleted unless cache_clear_all is called with a "wildcard".
>
> Yes, that's how it appears. The only DELETE I see there is inside of:
>
>   if ($cache_flush&&
>
> and I checked my site and it has no cache_flush_* entries in the
> variable table. I checked a few sites actually and none of them appear
> to have that.
>
> So are we back to my sneaking suspicion that a 'regular' site has no
> maximum expiration for cache? Seems that's what you wrote above also.
>

But it could be the result of the module you use to provide the 
schedule.  Is it calling the cache_clear_all() function?  The node_save 
function does.

-- 
Earnie
-- http://progw.com
-- http://www.for-my-kids.com