What is the limit of number of keys I can multi-get on memcache

Question

So in PHP we can do $memcache->get(array('a','b','c'));
I wonder what is the limit of keys before things break. Can I pass 1000 keys? 10000 keys?

I tried to find answer, but can't find anywhere.

Is there someone who have experience in passing large number of keys to do multi-get to memcache?

Answer 1

The Memcached extension supports at least 100,000 keys in a getMulti, given this test:

php > $data = array_map(function($v){ return 'x' . $v; }, range(1, 100000));
php > foreach($data as $d) { $memcached->add($d, $d); }
php > $multi = $memcached->getMulti($data);
php > echo is_array($multi);
1
php > echo count($multi);
100000

I tried to bump it up to a million, but I hit my configured PHP memory limit and promptly decided that if doing a getMulti of one hundred thousand items isn't good enough, you're probably abusing memcached.

Answer 2

There's no hard limit, but there will be different practical limits that will likely end up being application specific.