clearing caches individually (product, category, homepage, etc)

Question

is it possible to clear things like the products, category, homepage cache individually? If so, how?

Answer 1

EDIT: I should note that this isn't possible via Magento admin interface. You'd have to build/find an extension to add this functionality, else write a script with what I describe below.

-

Cleaning Cache Tags

Magento wraps all communication with the cache backend with Mage_Core_Model_Cache -> Mage::getSingleton('core/cache').

If you look at this class you can talk to the backend to remove cached entries using Mage_Core_Model_Cache::clean(array $tags). These cache tags should be given for your major Magento blocks. For example, look at Mage_Catalog_Model_Product:

class Mage_Catalog_Model_Product extends Mage_Catalog_Model_Abstract
{
    /**
     * Entity code.
     * Can be used as part of method name for entity processing
     */
    const ENTITY                 = 'catalog_product';

    const CACHE_TAG              = 'catalog_product';
    protected $_cacheTag         = 'catalog_product';
    protected $_eventPrefix      = 'catalog_product';
    protected $_eventObject      = 'product';
    protected $_canAffectOptions = false;
    ...

The const CACHE_TAG is what you'll be looking for. You can clear all product block cache using this tag, like so:

Mage::getSingleton('core/cache')->clean(array('catalog_product'));

As for categories, I don't know of any cache tags implemented for their view classes As Si Griffiths noted, you can use the catalog_category tags.

As for the homepage, which is a CMS page, the cache tag is actually derived from the CMS page model, Mage_Cms_Model_Page::CACHE_TAG. The block abstract (Mage_Core_Block_Abstract) has a method that lets you port over cache tags from a model (see Mage_Core_Block_Abstract::addModelTags). This pattern is also used for categories and products.

Working with FPC

As mentioned by both Si and myself, FPC adds a layer of complexity to dealing with cache that can't be resolved just by cleaning cache tags. FPC is a separate layer of caching that is stored separately.

To flush ALL FPC, you can use the following:

Enterprise_PageCache_Model_Cache::getCacheInstance()->flush()

Combining that with the above tag cleaning method, you should be able to programmatically get product/category pages to reflect changes. But this FPC command will clear FPC abroad. This is where things like "hole-punching" come into play, but I would say it's beyond the scope of this question and better left to others who have already explained it well:

http://www.kingletas.com/2012/09/how-does-magento-full-page-cache-works.html https://stackoverflow.com/a/9125519/1442685

Answer 2

Programatically as mentioned above by Rick cache entires can be removed by tag. Most are constructed by tag+id with a slight exception being CMS pages.

So for example:

Products: 'catalog_product' would remove all or 'catalog_product_someidnumeric' would remove that particular id. Categories: 'catalog_category' CMS pages: 'cms_page'

Now that relates to the block cache. FPC in enterprise by default is an all or nothing approach from what I remember. You can clean the lot or nothing. Now extensions for redis or varnish make targeted FPC cleans better but by default you can only clean the lot.

A little tip is the cache tag sometimes matches the class applied to the body tag :)