Well, most of those variables will never matter to an anon user and those are the only ones eligible for page cache. But still, you have a point. We discuss this at length at http://drupal.org/node/590614. I even argued same as you. Please discuss there. On Tue, Jan 12, 2010 at 10:09 AM, Ivan Sergio Borgonovo <mail@webthatworks.it> wrote:
Hi,
I saw a chance to improve the flexibility of D7 cache, with something that looks as a very small change.
I'm sorry if I'm missing something, but I'd really appreciate if someone will point out what's wrong with my proposal.
Substantially D7 doesn't serve cached pages if $_SESSION isn't empty as stated in drupal_page_get_cache docs (I couldn't find anymore where $_SESSION is tested...).
This limit the use of cache substantially. Nearly all users will have a not empty $_SESSION that will force regeneration of ALL the pages.
Currently core put in SESSION: 1) openid 2) user_overview_filter 3) dblog_overview_filter 4) node_overview_filter 5) clean_url 6) authorize_filetransfer_backends 7) authorize_operation 8) ignore_slave_server 9) update_manager_update_projects 10) authorize_results 11) update_results 12) messages 13) locale_translation_filter 14) maintenance_mode 15) update_success 16) updates_remaining 17) maintenance_mode 18) batch_form_state 19) my_batch_results 20) batches
Most of them shouldn't actually forbid the use of ALL cached pages. One way to retro-fit a more fine grained control over cache would be to add a field to all the SESSION items in the array
eg. $_SESSION['session_var'] = $stuff; $_SESSION['session_var']['cacheable'] = true;
And in spite of invalidating all cached pages we could check if there is any ['cacheable'] that is null/unset preserving current behaviour and giving a chance to exploit more the cache.
Then we could add the ['cacheable'] flag where it is safe a bit at a time.
If bootstrap_invoke_all('boot') in function _drupal_bootstrap_page_cache() could be anticipated we could even give a chance to modules that would like to control if the cache has to be used to fire. eg. don't serve cached pages for user coming from this IP, don't serve cached pages during these hours, always serve cached pages to these IP etc...
-- Ivan Sergio Borgonovo http://www.webthatworks.it