Cache should allow memcache multi_get for performance

[hans]

The get($id) method of the Cache library breaks when passed an array of keys. ($this->driver->get($id) returns an array, which errors out since if (substr($data, 0, 14) === '<{serialized}>') expects a string).

Memcache::get performance is enhanced when passed an array rather than multiple individual calls, as the requests can be made in parallel and often spread across multiple memcache servers.

[hans]

The get() and set() methods of the Cache library and its related drivers should be refactored so that serialization and unserialization takes place within the drivers when necessary. In the case of the memcache driver, serialization and unserialization would never be necessary since anything other than a string or int is automatically serialized and unserialized by the native Memcache methods. (This refactoring would also fix the issue described above with passing in an array.)

[dynom]

Patch to allow disabling pre-serializing, per driver. And disable it for the memcache driver

[dynom]

Geert and I discussed this during a Bughuntday meeting (The topic was Zend Framework, but Geert and I made it our own Kohana meeting ;-) ), the previously attached patch is partially the feature-request. It allows cache back ends to do their own serializing, however it does not fix the array parameter getting of data. Since this forces some active design changes.

e.g.: If $id is an array of two id's, like: $id = array('a/a','b/b');. How would the return value be like, if both are already arrays? The Id's are translated from / or \\ to = to keep valid key names, so returning a associative array might be inconsistent:

$cache->set('a/a', range(0,10));
$cache->set('b/b', range('a','z'));

var_dump( $cache->get(array('a/a','b/b')) );

// Return a-1, with the current translated id's
array(
 'a=a' => array(0,10),
 'b=b' => array('a','z')
)

// Return a-2, with the untranslated id's
array(
 'a/a' => array(0,10),
 'b/b' => array('a','z')
)

// Return n
array(
 0 => array(0,10),
 1 => array('a','z')
)

Return A-2, would be most favorable (for obvious reasons) and doable of the original id's will remain available when returning data. However it leads to a inconsistent return value when called with a single id.

Proposal to introduce a new method e.g.: getMultiple and possibly a counter part: setMultiple rather then changing the current set and get

[dynom]

Same as previous patch, only now with the proposal.

[Geert]

Memcache driver now takes care of seriliazing stuff itself, r3652.