libdrizzle sharding functions

So, we already have a list of servers in libdrizzled via the use of drizzle_con_add_server(). I propose adding a new function:

drizzle_con_st* drizzle_con_get_shard(const char* key, size_t length);

This would use a consistent hashing algorithm similar to libketama for memcached (http://www.last.fm/user/RJ/journal/2007/04/10/rz_libketama_-_a_consistent_hashing_algo_for_memcache_clients). This link has a better explanation of it:
http://www.mikeperham.com/2009/01/14/consistent-hashing-in-memcache-client/

Alternatively the hashing algorithm from memcached can be used (since it is BSD licensed)

This will return a relevent connection for a key. Using this algorithm will help limit the amount of re-sorting required when adding/removing servers.

Then in layers such as the PHP drizzle library we could add functionality to do something like:

$drizzle->shardQuery($key, $query);

Which would send the query straight to the shard.