Performance Schema events_waits_history_long Table
The events_waits_history_long table by default contains the ten thousand most recent completed wait events. This number can be adjusted by setting the performance_schema_events_waits_history_long_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 withTHREAD_IDuniquely 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. |
INDEX_NAME |
Name of the index, PRIMARY for the primary key, or NULL for no index used. |
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. |
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 are related tables.
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https://mariadb.com/kb/en/performance-schema-events_waits_history_long-table/