connect  ddl, localhost, root,,;
update performance_schema.setup_instruments set enabled='yes';
update performance_schema.setup_consumers set enabled='yes';
CREATE TABLE t1 (a serial, b varchar(255)) ENGINE=InnoDB;
BEGIN;
COMMIT;
SET DEBUG_SYNC = 'row_log_apply_before SIGNAL go WAIT_FOR gone';
ALTER TABLE t1 ADD INDEX(b), ALGORITHM=INPLACE;
connection default;
SET DEBUG_SYNC = 'now WAIT_FOR go';
SELECT DISTINCT object_name FROM performance_schema.events_waits_history_long
WHERE event_name LIKE '%wait%io%file%innodb%innodb_temp_file%';
object_name
tmp/Innodb Merge Temp File
SET DEBUG_SYNC = 'now SIGNAL gone';
connection ddl;
disconnect ddl;
connection default;
SET DEBUG_SYNC = 'RESET';
DROP TABLE t1;