Performance Schema Transaction Tables • SOURCE • TIMER_START ,  TIMER_END ,  TIMER_WAIT • ACCESS_MODE • ISOLATION_LEVEL • AUTOCOMMIT • NUMBER_OF_SAVEPOINTS ,  NUMBER_OF_ROLLBACK_TO_SAVEPOINT , NUMBER_OF_RELEASE_SAVEPOINT • OBJECT_INSTANCE_BEGIN • NESTING_EVENT_ID • NESTING_EVENT_TYPE •Primary key on ( THREAD_ID ,  EVENT_ID ) TRUNCATE TABLE  is permitted for the  events_transactions_current  table. It removes the rows. The  events_transactions_current  table has these indexes: The nesting event type. The value is  TRANSACTION ,  STATEMENT ,  STAGE , or  WAIT . ( TRANSACTION does not appear because transactions cannot be nested.) 4987 The  EVENT_ID  value of the event within which this event is nested. Unused. The number of  SAVEPOINT ,  ROLLBACK TO SAVEPOINT , and  RELEASE SAVEPOINT  statements issued during the transaction. Whether autcommit mode was enabled when the transaction started. The transaction isolation level. The value is  REPEATABLE READ ,  READ COMMITTED ,  READ UNCOMMITTED , or  SERIALIZABLE . The transaction access mode. The value is  READ WRITE  or  READ ONLY . For discussion of picoseconds as the unit for event times and factors that affect time values, see Section 27.4.1, “Performance Schema Event Timing” . If an event is produced from an instrument that has  TIMED = NO , timing information is not collected, and  TIMER_START ,  TIMER_END , and  TIMER_WAIT  are all  NULL . If an event has not finished,  TIMER_END  is the current timer value and  TIMER_WAIT  is the time elapsed so far ( TIMER_END − TIMER_START ). Timing information for the event. The unit for these values is picoseconds (trillionths of a second). The TIMER_START  and  TIMER_END  values indicate when event timing started and ended.  TIMER_WAIT  is the event elapsed time (duration). The name of the source file containing the instrumented code that produced the event and the line number in the file at which the instrumentation occurs. This enables you to check the source to determine exactly what code is involved.