BKA needs to be specifically enabled, there are mysql-test/t/*_jcl6.test tests that are a re-run of relevant tests with BKA. The rest of the testsuite won’t give much more coverage I’m afraid because BKA is about *big joins*, and we don’t have them in the testsuite. BKA has received some testing (and we found and fixed bugs) when Igor had run various DBT3-based tests with it. This has happened both before and after the mentioned UC session.