22.12.5 Performance Schema Stage Event Tables

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22.12.5.1 The events_stages_current Table

22.12.5.2 The events_stages_history Table

22.12.5.3 The events_stages_history_long Table

The Performance Schema instruments stages, which are steps during the statement-execution process, such as parsing a statement, opening a table, or performing a filesort operation. Stages correspond to the thread states displayed by SHOW PROCESSLIST or that are visible in the INFORMATION_SCHEMA.PROCESSLIST table. Stages begin and end when state values change.

Within the event hierarchy, wait events nest within stage events, which nest within statement events.

These tables store stage events:

• events_stages_current: The current stage event for each thread.

• events_stages_history: The most recent stage events that have ended per thread.

• events_stages_history_long: The most recent stage events that have ended globally (across all threads).

The following sections describe the stage event tables. There are also summary tables that aggregate information about stage events; see Section 22.12.9.2, “Stage Summary Tables”.

For more information about the relationship between the three stage event tables, see Section 22.9, “Performance Schema Tables for Current and Historical Events”.

Configuring Stage Event Collection

To control whether to collect stage events, set the state of the relevant instruments and consumers:

• The setup_instruments table contains instruments with names that begin with stage. Use these instruments to enable or disable collection of individual stage event classes.

• The setup_consumers table contains consumer values with names corresponding to the current and historical stage event table names. Use these consumers to filter collection of stage events.

The stage instruments are disabled by default. For example:

mysql> SELECT *
       FROM performance_schema.setup_instruments
       WHERE NAME RLIKE 'stage/sql/[a-c]';
+----------------------------------------------------+---------+-------+
| NAME                                               | ENABLED | TIMED |
+----------------------------------------------------+---------+-------+
| stage/sql/After create                             | NO      | NO    |
| stage/sql/allocating local table                   | NO      | NO    |
| stage/sql/altering table                           | NO      | NO    |
| stage/sql/committing alter table to storage engine | NO      | NO    |
| stage/sql/Changing master                          | NO      | NO    |
| stage/sql/Checking master version                  | NO      | NO    |
| stage/sql/checking permissions                     | NO      | NO    |
| stage/sql/checking privileges on cached query      | NO      | NO    |
| stage/sql/checking query cache for query           | NO      | NO    |
| stage/sql/cleaning up                              | NO      | NO    |
| stage/sql/closing tables                           | NO      | NO    |
| stage/sql/Connecting to master                     | NO      | NO    |
| stage/sql/converting HEAP to MyISAM                | NO      | NO    |
| stage/sql/Copying to group table                   | NO      | NO    |
| stage/sql/Copying to tmp table                     | NO      | NO    |
| stage/sql/copy to tmp table                        | NO      | NO    |
| stage/sql/Creating delayed handler                 | NO      | NO    |
| stage/sql/Creating sort index                      | NO      | NO    |
| stage/sql/creating table                           | NO      | NO    |
| stage/sql/Creating tmp table                       | NO      | NO    |
+----------------------------------------------------+---------+-------+

The stage consumers are disabled by default:

mysql> SELECT *
       FROM performance_schema.setup_consumers
       WHERE NAME LIKE 'events_stages%';
+----------------------------+---------+
| NAME                       | ENABLED |
+----------------------------+---------+
| events_stages_current      | NO      |
| events_stages_history      | NO      |
| events_stages_history_long | NO      |
+----------------------------+---------+

To control stage event collection at server startup, use lines like these in your my.cnf file:

• Enable:

  [mysqld]
  performance-schema-instrument='stage/%=ON'
  performance-schema-consumer-events-stages-current=ON
  performance-schema-consumer-events-stages-history=ON
  performance-schema-consumer-events-stages-history-long=ON

• Disable:

  [mysqld]
  performance-schema-instrument='stage/%=OFF'
  performance-schema-consumer-events-stages-current=OFF
  performance-schema-consumer-events-stages-history=OFF
  performance-schema-consumer-events-stages-history-long=OFF

To control stage event collection at runtime, update the setup_instruments and setup_consumers tables:

• Enable:

  UPDATE performance_schema.setup_instruments
  SET ENABLED = 'YES', TIMED = 'YES'
  WHERE NAME = 'stage/%';
  
  UPDATE performance_schema.setup_consumers
  SET ENABLED = 'YES'
  WHERE NAME LIKE 'events_stages%';

• Disable:

  UPDATE performance_schema.setup_instruments
  SET ENABLED = 'NO', TIMED = 'NO'
  WHERE NAME = 'stage/%';
  
  UPDATE performance_schema.setup_consumers
  SET ENABLED = 'NO'
  WHERE NAME LIKE 'events_stages%';

To collect only specific stage events, enable only the corresponding stage instruments. To collect stage events only for specific stage event tables, enable the stage instruments but only the stage consumers corresponding to the desired tables.

The setup_timers table contains a row with a NAME value of stage that indicates the unit for stage event timing. The default unit is NANOSECOND:

mysql> SELECT *
       FROM performance_schema.setup_timers
       WHERE NAME = 'stage';
+-------+------------+
| NAME  | TIMER_NAME |
+-------+------------+
| stage | NANOSECOND |
+-------+------------+

To change the timing unit, modify the TIMER_NAME value:

UPDATE performance_schema.setup_timers
SET TIMER_NAME = 'MICROSECOND'
WHERE NAME = 'stage';

For additional information about configuring event collection, see Section 22.3, “Performance Schema Startup Configuration”, and Section 22.4, “Performance Schema Runtime Configuration”.