10.4 Performance Schema Wait Event Tables

10.4.1 The events_waits_current Table

10.4.2 The events_waits_history Table

10.4.3 The events_waits_history_long Table

The Performance Schema instruments waits, which are events that take time. Within the event hierarchy, wait events nest within stage events, which nest within statement events, which nest within transaction events.

These tables store wait events:

• events_waits_current: The current wait event for each thread.

• events_waits_history: The most recent wait events that have ended per thread.

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

The following sections describe the wait event tables. There are also summary tables that aggregate information about wait events; see Section 10.20.1, “Wait Event Summary Tables”.

For more information about the relationship between the three wait event tables, see Performance Schema Tables for Current and Historical Events.

Configuring Wait Event Collection

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

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

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

Some wait instruments are enabled by default; others are disabled. For example:

mysql> SELECT NAME, ENABLED, TIMED
       FROM performance_schema.setup_instruments
       WHERE NAME LIKE 'wait/io/file/innodb%';
+-------------------------------------------------+---------+-------+
| NAME                                            | ENABLED | TIMED |
+-------------------------------------------------+---------+-------+
| wait/io/file/innodb/innodb_tablespace_open_file | YES     | YES   |
| wait/io/file/innodb/innodb_data_file            | YES     | YES   |
| wait/io/file/innodb/innodb_log_file             | YES     | YES   |
| wait/io/file/innodb/innodb_temp_file            | YES     | YES   |
| wait/io/file/innodb/innodb_arch_file            | YES     | YES   |
| wait/io/file/innodb/innodb_clone_file           | YES     | YES   |
+-------------------------------------------------+---------+-------+
mysql> SELECT NAME, ENABLED, TIMED
       FROM performance_schema.setup_instruments
       WHERE NAME LIKE 'wait/io/socket/%';
+----------------------------------------+---------+-------+
| NAME                                   | ENABLED | TIMED |
+----------------------------------------+---------+-------+
| wait/io/socket/sql/server_tcpip_socket | NO      | NO    |
| wait/io/socket/sql/server_unix_socket  | NO      | NO    |
| wait/io/socket/sql/client_connection   | NO      | NO    |
+----------------------------------------+---------+-------+

The wait consumers are disabled by default:

mysql> SELECT *
       FROM performance_schema.setup_consumers
       WHERE NAME LIKE 'events_waits%';
+---------------------------+---------+
| NAME                      | ENABLED |
+---------------------------+---------+
| events_waits_current      | NO      |
| events_waits_history      | NO      |
| events_waits_history_long | NO      |
+---------------------------+---------+

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

• Enable:

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

• Disable:

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

To control wait 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 LIKE 'wait/%';
  UPDATE performance_schema.setup_consumers
  SET ENABLED = 'YES'
  WHERE NAME LIKE 'events_waits%';

• Disable:

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

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

For additional information about configuring event collection, see Chapter 4, Performance Schema Startup Configuration, and Chapter 5, Performance Schema Runtime Configuration.