Performance Schema events_waits_history Table

The events_waits_history table by default contains the ten most recent completed wait events per thread. This number can be adjusted by setting the performance_schema_events_waits_history_size system variable when the server starts up.

The table structure is identical to the events_waits_current table structure, and contains the following columns:

Column Description
THREAD_ID Thread associated with the event. Together with EVENT_ID uniquely identifies the row.
EVENT_ID Thread's current event number at the start of the event. Together with THREAD_ID uniquely identifies the row.
END_EVENT_ID NULL when the event starts, set to the thread's current event number at the end of the event.
EVENT_NAME Event instrument name and a NAME from the setup_instruments table
SOURCE Name and line number of the source file containing the instrumented code that produced the event.
TIMER_START Value in picoseconds when the event timing started or NULL if timing is not collected.
TIMER_END Value in picoseconds when the event timing ended, or NULL if timing is not collected.
TIMER_WAIT Value in picoseconds of the event's duration or NULL if timing is not collected.
SPINS Number of spin rounds for a mutex, or NULL if spin rounds are not used, or spinning is not instrumented.
OBJECT_SCHEMA Name of the schema that contains the table for table I/O objects, otherwise NULL for file I/O and synchronization objects.
OBJECT_NAME File name for file I/O objects, table name for table I/O objects, the socket's IP:PORT value for a socket object or NULL for a synchronization object.
OBJECT_TYPE FILE for a file object, TABLE or TEMPORARY TABLE for a table object, or NULL for a synchronization object.
OBJECT_INSTANCE_BEGIN Address in memory of the object.
INDEX NAME Name of the index, PRIMARY for the primary key, or NULL for no index used.
NESTING_EVENT_ID EVENT_ID of event within which this event nests.
NESTING_EVENT_TYPE Nesting event type. Either statement, stage or wait.
OPERATION Operation type, for example read, write or lock
NUMBER_OF_BYTES Number of bytes that the operation read or wrote, or NULL for table I/O waits.
FLAGS Reserved for use in the future.

It is possible to empty this table with a TRUNCATE TABLE statement.

events_waits_current and events_waits_history_long are related tables.

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