i set auto_initialize to true
configured the session to use the database
run the welcome controller a few time but no db query was made
shouldn't be at least 1db request ? or i don't understand correctly what auto_initialize dose
That only happens if you load the Session class, which the welcome controller doesn't do.
It get's loaded if you specify it as autoload in your app's config, or as soon as you call one of the static methods.