- 21.9.4 Performance Schema Stage Event Tables
- 21.9.4.1 The events_stages_current Table
- 21.9.4.2 The events_stages_history Table
- 21.9.4.3 The events_stages_history_long Table
The events_stages_current table
contains current stage events, one row per thread showing the
current status of the thread's most recent monitored stage
event.
The events_stages_current table
can be truncated with TRUNCATE
TABLE.
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, up to a fixed
number of rows.
The events_stages_current table
has these columns:
THREAD_IDThe thread associated with the event. The
THREAD_IDandEVENT_IDvalues taken together form a primary key that uniquely identifies the row. No two rows will have the same pair of values.EVENT_IDThe thread current event number when the event starts.
END_EVENT_IDThis column is set to
NULLwhen the event starts, and updated to the thread current event number when the event ends. This column was added in MySQL 5.6.4.EVENT_NAMEThe name of the instrument that produced the event. This is a
setup_instruments.NAMEvalue. Instrument names have multiple parts and form a hierarchy, as discussed in Section 21.4, “Performance Schema Instrument Naming Conventions”.SOURCEThe 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_WAITTiming information for the event. The unit for these values is picoseconds (trillionths of a second). The
TIMER_STARTandTIMER_ENDvalues indicate when event timing started and ended.TIMER_WAITis the event elapsed time (duration).If an event has not finished,
TIMER_ENDandTIMER_WAITareNULL.If an event is produced from an instrument that has
TIMED = NO, timing information is not collected, andTIMER_START,TIMER_END, andTIMER_WAITare allNULL.For discussion of picoseconds as the unit for event times and factors that affect time values, see Section 21.2.3.1, “Performance Schema Event Timing”.
NESTING_EVENT_IDThe
EVENT_IDvalue of the event within which this event is nested. The nesting event for a stage event is usually a statement event.NESTING_EVENT_TYPEThe nesting event type. The value is
statement,stage, orwait.
The events_stages_current table
was added in MySQL 5.6.3.
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