Hi Elena, We're going to make the following enabled by default: @@optimizer_switch='semijoin_with_cache=on,outer_join_with_cache=on' @@join_cache_level=2 Could you please make a test run with these settings? It is important to test revision>=3337 (just pushed it), because it has a change in the optimizer which makes it choose semijoin+join_cache execution plans much more often. BR Sergei -- Sergei Petrunia, Software Developer Monty Program AB, http://askmonty.org Blog: http://s.petrunia.net/blog