query resultset caching

Hi all,

I would like to know if and eventually how suitecrm cache resultsets of db queries.
As I can see it supports many caching systems.
Does It make sense to mix them? How they will be used?

$sugar_config['http_referer']['list'][0] = 'xxx';
$sugar_config['external_cache']['redis']['host'] = '127.0.0.1';
$sugar_config['external_cache_disabled_apc'] = true;
$sugar_config['external_cache_disabled_memcached'] = true;
$sugar_config['external_cache_disabled_smash'] = true;
$sugar_config['external_cache_disabled_zend'] = true;

Thank you!
Jacopo