CREATE TABLE t1 (a INT NOT NULL) ENGINE=InnoDB STATS_PERSISTENT=0; connect ddl,localhost,root; SET DEBUG_SYNC='after_trx_committed_in_memory SIGNAL stuck WAIT_FOR ever EXECUTE 2'; ALTER TABLE t1 ADD PRIMARY KEY(a); connection default; SET DEBUG_SYNC='now WAIT_FOR stuck'; SET DEBUG_SYNC='now SIGNAL ever'; SET DEBUG_SYNC='now WAIT_FOR stuck'; SET GLOBAL innodb_log_checkpoint_now=ON; # restart disconnect ddl; SHOW CREATE TABLE t1; Table Create Table t1 CREATE TABLE `t1` ( `a` int(11) NOT NULL, PRIMARY KEY (`a`) ) ENGINE=InnoDB DEFAULT CHARSET=latin1 STATS_PERSISTENT=0 SELECT * FROM t1; a DROP TABLE t1; InnoDB 0 transactions not purged