expiry

[Joshua Thijssen]

> Something like this then:
>
> memcache->set($key, $val, $expiry);
> memcache->get($key);
> memcache->set($key, $val, $expiry);

Yes, which is the way we do it now, but of course this creates a lot of
overhead. I'm not sure if it's possible to do it, but on a item-read,
the expiry-timestamp could be updated by adding the (relative)
expiry-time to the current time.

The main advantage I think this would have, is that you can add many
items to your cache, but that only the currently mostly-used items are
kept, thus saving a lot of memory.
For instance: You store user comments for blog-articles inside the
cache. The comments that are not read in the last 7 days could be
removed from the cache. Even if somebody reads the comment, it is
fetched from DB, stored in cache again, until it expires again.