View cache and cache blocks #

This page is for website creators who template pages and need them both fast and current. Two caches do most of the work: the content view cache keeps the rendered main area of each page, and cache blocks keep parts of templates such as menus.

Contents #

1. The content view cache
2. What a publish clears
3. Cache blocks
4. Keys, expiry and subtree expiry
5. Debugging stale output

The content view cache #

site.ini [ContentSettings]:

A cached view is kept per node, view mode, language, siteaccess, user's roles and limitations, view parameters and layout. The pagelayout is not part of it: it runs every time, which is why it uses cache blocks.

What a publish clears #

Publishing an object clears the cache of its own nodes, their parents, and related objects, as settings/viewcache.ini [ViewCacheSettings] says: ClearRelationTypes[] (common, reverse_common, reverse_embedded) decides which relations count; SmartCacheClear adds rules per class. A page that lists content from far away in the tree (a front page listing news) is not cleared automatically unless a rule says so; use subtree expiry in its cache blocks, or a smart cache clear rule.

Cache blocks #

{cache-block keys=array( $module_result.uri, $current_user.contentobject_id )}
  ... expensive menu ...
{/cache-block}

The block's output is stored and reused while its keys match and it has not expired. Published content clears all template block caches by default, so a new folder appears in menus.

Keys, expiry and subtree expiry #

A front page news list:

{cache-block subtree_expiry='/News' expiry=0}
  {foreach fetch( 'content', 'list', hash( 'parent_node_id', 58, 'limit', 5, 'sort_by', array( 'published', false() ) ) ) as $item}
    {node_view_gui content_node=$item view='line'}
  {/foreach}
{/cache-block}

Never cache output that differs per user (a greeting, a basket count) without the user in the keys.

Debugging stale output #

The debug bar shows which caches were used for a page (Exp debug bar).

Related pages #

• Performance and caching for websites
• Caches
• Caching in applications
• Free documentation: this page is free to copy, translate and improve under the GNU FDL 1.3.