race condition during INSERT into db, in cache_set() ?

i am using memcache on a fairly high traffic drupal site, and watchdog is showing me a bunch of php warnings (and they get dumped out to the user as well!) of the type: Duplicate entry 'foobar' for key 1 query: cache_set INSERT INTO cache (data, created, expire, headers, serialized, cid) VALUES, and this seems to be coming from memcache.db.inc, in the cache_set() function.

i notice that the analogous cache_set() in the drupal core cache.inc has a db_lock_table() around the update of the cache table.

is there any reason why memcache.db.inc is *not* doing the lock on the table?

what i am assuming is happening is that the multiple processes are doing the delete/insert in cache_set() and one deletes, the other deletes, then the first inserts, and the second one tries also, and gets the warning.

has anyone else seen this problem? btw, i am sure its this insert in memcache.db.inc causing the error cuz i changed the case of the "INSERT INTO" and the case changes in the watchdog message, heh.

thanks!
-jon