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MySQL 5.6 Reference Manual  /  ...  /  Query Profiling Using Performance Schema

22.17.1 Query Profiling Using Performance Schema

The following example demonstrates how to use Performance Schema statement events and stage events to retrieve data comparable to profiling information provided by SHOW PROFILES and SHOW PROFILE statements.

In this example, statement and stage event data is collected in the events_statements_history_long and events_stages_history_long tables. On a busy server with many active foreground threads, data could age out of the history tables before you are able to retrieve the information you want to analyze. If you encounter this problem, options include:

Performance Schema displays event timer information in picoseconds (trillionths of a second) to normalize timing data to a standard unit. In the following example, TIMER_WAIT values are divided by 1000000000000 to show data in units of seconds. Values are also truncated to 6 decimal places to display data in the same format as SHOW PROFILES and SHOW PROFILE statements.

  1. Ensure that statement and stage instrumentation is enabled by updating the setup_instruments table. Some instruments may already be enabled by default.

    mysql> UPDATE performance_schema.setup_instruments SET ENABLED = 'YES', TIMED = 'YES'
           WHERE NAME LIKE '%statement/%';
    
    mysql> UPDATE performance_schema.setup_instruments SET ENABLED = 'YES', TIMED = 'YES'
           WHERE NAME LIKE '%stage/%';
  2. Ensure that events_statements_* and events_stages_* consumers are enabled. Some consumers may already be enabled by default.

    mysql> UPDATE performance_schema.setup_consumers SET ENABLED = 'YES'
           WHERE NAME LIKE '%events_statements_%';
    
    mysql> UPDATE performance_schema.setup_consumers SET ENABLED = 'YES'
           WHERE NAME LIKE '%events_stages_%';
  3. Run the statement that you want to profile. For example:

    mysql> SELECT * FROM employees.employees WHERE emp_no = 10001;
    +--------+------------+------------+-----------+--------+------------+
    | emp_no | birth_date | first_name | last_name | gender | hire_date |
    +--------+------------+------------+-----------+--------+------------+
    |  10001 | 1953-09-02 | Georgi     | Facello   | M      | 1986-06-26 |
    +--------+------------+------------+-----------+--------+------------+
  4. Identify the EVENT_ID of the statement by querying the events_statements_history_long table. This step is similar to running SHOW PROFILES to identify the Query_ID. The following query produces output similar to SHOW PROFILES:

    mysql> SELECT EVENT_ID, TRUNCATE(TIMER_WAIT/1000000000000,6) as Duration, SQL_TEXT
           FROM performance_schema.events_statements_history_long WHERE SQL_TEXT like '%10001%';
    +----------+----------+--------------------------------------------------------+
    | event_id | duration | sql_text                                               |
    +----------+----------+--------------------------------------------------------+
    |       31 | 0.028310 | SELECT * FROM employees.employees WHERE emp_no = 10001 |
    +----------+----------+--------------------------------------------------------+
  5. Query the events_stages_history_long table to retrieve the statement's stage events. Stages are linked to statements using event nesting. Each stage event record has a NESTING_EVENT_ID column that contains the EVENT_ID of the parent statement.

    mysql> SELECT event_name AS Stage, TRUNCATE(TIMER_WAIT/1000000000000,6) AS Duration
           FROM performance_schema.events_stages_history_long WHERE NESTING_EVENT_ID=31;
    +--------------------------------+----------+
    | Stage                          | Duration |
    +--------------------------------+----------+
    | stage/sql/starting             | 0.000080 |
    | stage/sql/checking permissions | 0.000005 |
    | stage/sql/Opening tables       | 0.027759 |
    | stage/sql/init                 | 0.000052 |
    | stage/sql/System lock          | 0.000009 |
    | stage/sql/optimizing           | 0.000006 |
    | stage/sql/statistics           | 0.000082 |
    | stage/sql/preparing            | 0.000008 |
    | stage/sql/executing            | 0.000000 |
    | stage/sql/Sending data         | 0.000017 |
    | stage/sql/end                  | 0.000001 |
    | stage/sql/query end            | 0.000004 |
    | stage/sql/closing tables       | 0.000006 |
    | stage/sql/freeing items        | 0.000272 |
    | stage/sql/cleaning up          | 0.000001 |
    +--------------------------------+----------+

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