MySQL 8.0 Reference Manual Including MySQL NDB Cluster 8.0
The events_stages_current table
contains current stage events. The table stores one row per
thread showing the current status of the thread's most recent
monitored stage event, so there is no system variable for
configuring the table size.
Of the tables that contain stage event rows,
events_stages_current is the most
fundamental. Other tables that contain stage event rows are
logically derived from the current events. For example, the
events_stages_history and
events_stages_history_long tables
are collections of the most recent stage events that have
ended, up to a maximum number of rows per thread and globally
across all threads, respectively.
For more information about the relationship between the three stage event tables, see Section 29.9, “Performance Schema Tables for Current and Historical Events”.
For information about configuring whether to collect stage events, see Section 29.12.5, “Performance Schema Stage Event Tables”.
The events_stages_current table
has these columns:
THREAD_ID, EVENT_ID
The thread associated with the event and the thread
current event number when the event starts. The
THREAD_ID and
EVENT_ID values taken together uniquely
identify the row. No two rows have the same pair of
values.
END_EVENT_ID
This column is set to NULL when the
event starts and updated to the thread current event
number when the event ends.
EVENT_NAME
The name of the instrument that produced the event. This
is a NAME value from the
setup_instruments table.
Instrument names may have multiple parts and form a
hierarchy, as discussed in
Section 29.6, “Performance Schema Instrument Naming Conventions”.
SOURCE
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.
TIMER_START,
TIMER_END,
TIMER_WAIT
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).
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).
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.
For discussion of picoseconds as the unit for event times and factors that affect time values, see Section 29.4.1, “Performance Schema Event Timing”.
WORK_COMPLETED,
WORK_ESTIMATED
These columns provide stage progress information, for
instruments that have been implemented to produce such
information. WORK_COMPLETED indicates
how many work units have been completed for the stage, and
WORK_ESTIMATED indicates how many work
units are expected for the stage. For more information,
see Stage Event Progress Information.
NESTING_EVENT_ID
The EVENT_ID value of the event within
which this event is nested. The nesting event for a stage
event is usually a statement event.
NESTING_EVENT_TYPE
The nesting event type. The value is
TRANSACTION,
STATEMENT, STAGE, or
WAIT.
The events_stages_current table
has these indexes:
Primary key on (THREAD_ID,
EVENT_ID)
TRUNCATE TABLE is permitted for
the events_stages_current table.
It removes the rows.