delete cache by prefix in apc / memcache / eaccelerator

Question

Let's assume I have these variables saved in apc, memcached and eaccelerator:

• article_1_0
• article_1_1
• article_3_2
• article_3_3
• article_2_4

How can I delete all cached variables that starts with article_3_ (they can reach up to 10000) ?

is there any way to list the cached variables ?

Answer 1

The slow solution

For APC:

$iterator = new APCIterator('user', '#^article_3_#', APC_ITER_KEY);
foreach($iterator as $entry_name) {
    apc_delete($entry_name);
}

For eaccelerator:

foreach(eaccelerator_list_keys() as $name => $infos) {
    if (preg_match('#^article_3_#', $name)) {
        eaccelerator_rm($name);
    }
}

For memcached, look at @rik's answer

The proper solution

The general solution for expiring multiple keys at once is to namespace them. For expiring them, you just have to change the namespace:

Say you have a group of keys "article_3_1", "article_3_2", .... You can store them like this:

$ns = apc_fetch('article_3_namespace');
apc_store($ns."_article_3_1", $value);
apc_store($ns."_article_3_2", $value);

Fetch them like this:

$ns = apc_fetch('article_3_namespace');
apc_fetch($ns."_article_3_1");

And expire them all by just incrementing the namespace:

apc_inc('article_3_namespace');

Answer 2

Although the docs say APCIterator is available in apc >= 3.1.1, I'm on several systems that claim to have apc 3.1.9, however there is no APCIterator present. If you don't have APCIterator at your disposal, give something like this a whirl:

$aCacheInfo = apc_cache_info('user');

foreach($aCacheInfo['cache_list'] as $_aCacheInfo)
    if(strpos($_aCacheInfo['info'], 'key_prefix:') === 0)
        apc_delete($_aCacheInfo['info']);

In this example we're checking for a prefix in the key, but you could use preg_match et. al and achieve something closer to what APCIterator provides.

Answer 3

There is a way to retrieve all keys from memcache but it's very expensive.

Answer 4

If there is possibility to use alternatives for memcached, scache supports structured keyspaces. With it you could store data to nested paths :

scache_shset($conn, 'article/1/0', $data10);
scache_shset($conn, 'article/3/0', $data30);
scache_shset($conn, 'article/3/1', $data31);

and eventually destroy data by deleting the parent node

scache_shunset($conn, 'article/3');

Answer 5

There is an APCIterator which helps you search through the keys in APC. Instantiate the APCIterator.

APCIterator::valid() means that there are keys still to iterate trough. APCIterator::key() returns you the apc key. APCIterator::next() moves the iterator position to the next item.

// APC
$iterator = new APCIterator('user', '/^article_3_/');

while($iterator->valid()) {
     apc_delete($iterator->key());
     // You can view the info for this APC cache value and so on by using 
     // $iterator->current() which is array
     $iterator->next();
}

For memcache you can use Memcached and use getAllKeys method

// Memcached 
$m = new Memcached();
$m->addServer('mem1.domain.com', 11211);

$items = $m->getAllKeys();

foreach($items as $item) {
    if(preg_match('#^article_3_#', $item)) {
        $m->delete($item);
    }
}