MYSQL PERFORMANCE_SCHEMA HINTS

ACCOUNTS NOT PROPERLY CLOSING CONNECTIONS [ 1 ]

Works since 5.6

SELECT ess.user, ess.host
     , (a.total_connections - a.current_connections) - ess.count_star as not_closed
     , ((a.total_connections - a.current_connections) - ess.count_star) * 100 /
       (a.total_connections - a.current_connections) as pct_not_closed
  FROM performance_schema.events_statements_summary_by_account_by_event_name ess
  JOIN performance_schema.accounts a on (ess.user = a.user and ess.host = a.host)
 WHERE ess.event_name = 'statement/com/quit'
   AND (a.total_connections - a.current_connections) > ess.count_star
;

UNUSED INDEXES [ 2 ]

Works since 5.6

SELECT object_schema, object_name, index_name
  FROM performance_schema.table_io_waits_summary_by_index_usage
 WHERE index_name IS NOT NULL
   AND count_star = 0
 ORDER BY object_schema, object_name
;

WHO CREATED TEMPORARY (DISK) TABLES

Works since 5.6

SELECT user, host, event_name, count_star AS cnt, sum_created_tmp_disk_tables AS tmp_disk_tables, sum_created_tmp_tables AS tmp_tables
  FROM performance_schema.events_statements_summary_by_account_by_event_name
 WHERE sum_created_tmp_disk_tables > 0
    OR sum_created_tmp_tables > 0
;

SELECT schema_name, substr(digest_text, 1, 40) AS statement, count_star AS cnt, sum_created_tmp_disk_tables AS tmp_disk_tables, sum_created_tmp_tables AS tmp_tables
  FROM performance_schema.events_statements_summary_by_digest
 WHERE sum_created_tmp_disk_tables > 0
    OR sum_created_tmp_tables > 0
;

ACCOUNTS WHICH NEVER CONNECTED SINCE LAST START-UP [ 3 ]

Works since 5.6

SELECT DISTINCT m_u.user, m_u.host
  FROM mysql.user m_u
  LEFT JOIN performance_schema.accounts ps_a ON m_u.user = ps_a.user AND m_u.host = ps_a.host
 WHERE ps_a.user IS NULL
ORDER BY m_u.user
;

USERS WHICH NEVER CONNECTED SINCE LAST START-UP

Works since 5.6

SELECT DISTINCT m_u.user
  FROM mysql.user m_u
  LEFT JOIN performance_schema.users ps_u ON m_u.user = ps_u.user
 WHERE ps_u.user IS NULL
 ORDER BY m_u.user
;

TOTALLY UNUSED ACCOUNTS (NEVER CONNECTED SINCE LAST RESTART AND NOT USED TO CHECK STORED PROGRAM OR VIEW PRIVILEGES) SINCE LAST START-UP

Works since 5.6

SELECT DISTINCT m_u.user, m_u.host
  FROM mysql.user m_u
  LEFT JOIN performance_schema.accounts ps_a ON m_u.user = ps_a.user AND ps_a.host = m_u.host
  LEFT JOIN information_schema.views is_v ON is_v.DEFINER = CONCAT(m_u.User, '@', m_u.Host) AND is_v.security_type = 'DEFINER'
  LEFT JOIN information_schema.routines is_r ON is_r.DEFINER = CONCAT(m_u.User, '@', m_u.Host) AND is_r.security_type = 'DEFINER'
  LEFT JOIN information_schema.events is_e ON is_e.definer = CONCAT(m_u.user, '@', m_u.host)
  LEFT JOIN information_schema.triggers is_t ON is_t.definer = CONCAT(m_u.user, '@', m_u.host)
 WHERE ps_a.user IS NULL
   AND is_v.definer IS NULL
   AND is_r.definer IS NULL
   AND is_e.definer IS NULL
   AND is_t.definer IS NULL
 ORDER BY m_u.user, m_u.host
;

SHOW FULL PROCESSLIST

Works since 5.5 (5.1?)

But with filter on Sleep and sorting by time to find the evil query...

SELECT id, user, host, db, command, time, state, LEFT(info, 80) AS info
  FROM information_schema.processlist
 WHERE command NOT IN ('Sleep', 'Binlog Dump')
 ORDER BY time ASC
;

Non blocking version, since 5.6:

SELECT PROCESSLIST_ID AS id, PROCESSLIST_USER AS user, PROCESSLIST_HOST AS host, PROCESSLIST_DB AS db
     , PROCESSLIST_COMMAND AS command, PROCESSLIST_TIME AS time, PROCESSLIST_STATE AS state, LEFT(PROCESSLIST_INFO, 80) AS info
  FROM performance_schema.threads
 WHERE PROCESSLIST_ID IS NOT NULL
   AND PROCESSLIST_COMMAND NOT IN ('Sleep', 'Binlog Dump')
 ORDER BY PROCESSLIST_TIME ASC
;

STORAGE ENGINES PER SCHEMA

For defining backup strategy, preparing migration to InnoDB or Galera Cluster for MySQL, etc.

Works since 5.5 (5.1?)

SELECT table_schema AS `schema`, engine, COUNT(*) AS `tables`
     , ROUND(SUM(data_length)/1024/1024, 0) AS data_mb, ROUND(SUM(index_length)/1024/1024, 0) index_mb
  FROM information_schema.tables
 WHERE table_schema NOT IN ('mysql', 'information_schema', 'performance_schema')
   AND engine IS NOT NULL
 GROUP BY table_schema, engine
;
+---------------------+--------+--------+---------+----------+
| schema              | engine | tables | data_mb | index_mb |
+---------------------+--------+--------+---------+----------+
| mantis              | MyISAM |     31 |       0 |        0 |
| mpm                 | InnoDB |      3 |       0 |        0 |
| mysql_sequences     | InnoDB |      2 |       0 |        0 |
| mysql_sequences     | MEMORY |      1 |       0 |        0 |
| otrs                | InnoDB |     73 |      13 |        4 |
| quartz              | InnoDB |     12 |       0 |        0 |
| tracking            | MyISAM |      1 |       0 |        0 |
+---------------------+--------+--------+---------+----------+

TABLES WITHOUT A PRIMARY KEY

Galera Cluster, InnoDB, M/S replication with row based replication does not work well with tables without a Primary Key. To find those the following query helps:

Works since 5.5 (5.1?)

SELECT DISTINCT t.table_schema, t.table_name
  FROM information_schema.tables AS t
  LEFT JOIN information_schema.columns AS c ON t.table_schema = c.table_schema AND t.table_name = c.table_name AND c.column_key = "PRI"
 WHERE t.table_schema NOT IN ('information_schema', 'mysql', 'performance_schema')
   AND c.table_name IS NULL AND t.table_type != 'VIEW'
;
+--------------+--------------------+
| table_schema | table_name         |
+--------------+--------------------+
| test         | t_wo_pk            |
| test         | t_wo_pk_with_Index |
+--------------+--------------------+

BAD SQL QUERIES OF USERS

Sometimes it could be interesting to find users who do evil SQL Queries which do for examplecreated_tmp_disk_tables, select_full_join, select_range_check or sort_merge_passes. Those can be found as follows:

SELECT user, host, event_name
     , sum_created_tmp_disk_tables AS tmp_disk_tables
     , sum_select_full_join AS full_join
     , sum_select_range_check AS range_check
     , sum_sort_merge_passes AS sort_merge
  FROM performance_schema.events_statements_summary_by_account_by_event_name
 WHERE sum_created_tmp_disk_tables > 0
    OR sum_select_full_join > 0
    OR sum_select_range_check > 0
    OR sum_sort_merge_passes > 0
 ORDER BY sum_sort_merge_passes DESC
 LIMIT 10
;        

+-------+-------------+---------------+-----------------+-----------+-------------+------------+
| user  | host        | event_name    | tmp_disk_tables | full_join | range_check | sort_merge |
+-------+-------------+---------------+-----------------+-----------+-------------+------------+
| user1 | 192.168.0.3 | insert_select |               0 |      7033 |           0 |      10947 |
| user2 | 192.168.0.4 | insert_select |               0 |      6837 |           0 |      10792 |
| user1 | 192.168.0.1 | select        |        10742308 |      2095 |       23061 |         16 |
| user2 | 192.168.0.2 | select        |        10958067 |      2639 |       23162 |         14 |
+-------+-------------+---------------+-----------------+-----------+-------------+------------+

SHOW PROFILE IN PERFORMANCE_SCHEMA

On systems with heavy traffic the PERFORMANCE_SCHEMA tables might be too small.

mysql> SHOW GLOBAL VARIABLES LIKE 'perf%events%stage%hist%long%';
+----------------------------------------------------+-------+
| Variable_name                                      | Value |
+----------------------------------------------------+-------+
| performance_schema_events_stages_history_long_size | 10000 |
+----------------------------------------------------+-------+

mysql> pager grep history_long
mysql> SHOW ENGINE PERFORMANCE_SCHEMA STATUS;
| performance_schema | events_waits_history_long.row_size       | 184      |
| performance_schema | events_waits_history_long.row_count      | 1000     |
| performance_schema | events_waits_history_long.memory         | 184000   |
| performance_schema | events_stages_history_long.row_size      | 88       |
| performance_schema | events_stages_history_long.row_count     | 1000     |
| performance_schema | events_stages_history_long.memory        | 88000    |
| performance_schema | events_statements_history_long.row_size  | 3024     |
| performance_schema | events_statements_history_long.row_count | 1000     |
| performance_schema | events_statements_history_long.memory    | 3024000  |

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/%';
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_%';

mysql> SELECT ;

mysql> SELECT eshl.event_id AS Query_ID, TRUNCATE(eshl.timer_wait/1000000000000, 6) as Duration
     , LEFT(eshl.sql_text, 120) AS Query
  FROM performance_schema.events_statements_history_long AS eshl
  JOIN performance_schema.threads AS t ON t.thread_id = eshl.thread_id
 WHERE t.processlist_id = CONNECTION_ID();
+----------+-----------+-------------------------+
| Query_ID | Duration  | Query                   |
+----------+-----------+-------------------------+
|       12 | 13.560737 | select * from test.test |
+----------+-----------+-------------------------+

mysql> SELECT event_name AS Stage, TRUNCATE(timer_wait/1000000000000,6) AS Duration
  FROM performance_schema.events_stages_history_long
 WHERE nesting_event_id = 12;
+--------------------------------+-----------+
| Stage                          | Duration  |
+--------------------------------+-----------+
| stage/sql/starting             |  0.000043 |
| stage/sql/checking permissions |  0.000004 |
| stage/sql/Opening tables       |  0.002700 |
| stage/sql/init                 |  0.000025 |
| stage/sql/System lock          |  0.000009 |
| stage/sql/optimizing           |  0.000002 |
| stage/sql/statistics           |  0.000014 |
| stage/sql/preparing            |  0.000013 |
| stage/sql/executing            |  0.000000 |
| stage/sql/Sending data         | 13.557683 |
| stage/sql/end                  |  0.000002 |
| stage/sql/query end            |  0.000008 |
| stage/sql/closing tables       |  0.000006 |
| stage/sql/freeing items        |  0.000215 |
| stage/sql/cleaning up          |  0.000001 |
+--------------------------------+-----------+

SELECT, INSERT, UPDATE AND DELETE PER TABLE

Sometimes it is interesting to know how many SELECT, INSERT, UPDATE or DELETE (DML) statementes have been exectuted against a specifict table (for example for OPTIMZE TABLE). This can be found as follows:

Works since MySQL 5.6

SELECT object_type, object_schema, object_name
     , count_star, count_read, count_write, count_fetch
     , count_insert, count_update, count_delete
  FROM performance_schema.table_io_waits_summary_by_table
 WHERE count_star > 0
;

SELECT object_type, object_schema, object_name, index_name
     , count_star, count_read, count_write, count_fetch
     , count_insert, count_update, count_delete
  FROM performance_schema.table_io_waits_summary_by_index_usage
 WHERE count_star > 0
;

TOP LONG RUNNING QUERIES

Works since MySQL 5.6

UPDATE setup_consumers SET enabled = 1 WHERE name = 'events_statements_history_long';

SELECT left(digest_text, 64)
     , ROUND(SUM(timer_end-timer_start)/1000000000, 1) AS tot_exec_ms
     , ROUND(SUM(timer_end-timer_start)/1000000000/COUNT(*), 1) AS avg_exec_ms
     , ROUND(MIN(timer_end-timer_start)/1000000000, 1) AS min_exec_ms
     , ROUND(MAX(timer_end-timer_start)/1000000000, 1) AS max_exec_ms
     , ROUND(SUM(timer_wait)/1000000000, 1) AS tot_wait_ms
     , ROUND(SUM(timer_wait)/1000000000/COUNT(*), 1) AS avg_wait_ms
     , ROUND(MIN(timer_wait)/1000000000, 1) AS min_wait_ms
     , ROUND(MAX(timer_wait)/1000000000, 1) AS max_wait_ms
     , ROUND(SUM(lock_time)/1000000000, 1) AS tot_lock_ms
     , ROUND(SUM(lock_time)/1000000000/COUNT(*), 1) AS avglock_ms
     , ROUND(MIN(lock_time)/1000000000, 1) AS min_lock_ms
     , ROUND(MAX(lock_time)/1000000000, 1) AS max_lock_ms
     , MIN(LEFT(DATE_SUB(NOW(), INTERVAL (isgs.VARIABLE_VALUE - TIMER_START*10e-13) second), 19)) AS first_seen
     , MAX(LEFT(DATE_SUB(NOW(), INTERVAL (isgs.VARIABLE_VALUE - TIMER_START*10e-13) second), 19)) AS last_seen
     , COUNT(*) as cnt
  FROM events_statements_history_long
  JOIN information_schema.global_status AS isgs
 WHERE isgs.variable_name = 'UPTIME'
 GROUP BY LEFT(digest_text,64)
 ORDER BY tot_exec_ms DESC
;

+------------------------------------------------------------------+-------------+-------------+-------------+---------------------+---------------------+-----+
| left(digest_text, 64)                                            | tot_exec_ms | tot_wait_ms | tot_lock_ms | first_seen          | last_seen           | cnt |
+------------------------------------------------------------------+-------------+-------------+-------------+---------------------+---------------------+-----+
| INSERT INTO `test` SELECT ? , DATA , ? FROM `test`               |     50493.5 |     50493.5 |        26.3 | 2015-11-12 16:41:35 | 2015-11-12 16:42:04 |  20 |
| SELECT LEFT ( `digest_text` , ? ) , `ROUND` ( SUM ( `timer_end`  |     14434.6 |     14434.6 |        25.8 | 2015-11-12 16:48:44 | 2015-11-12 17:07:15 |   6 |
| SELECT * FROM `test`                                             |      7483.0 |      7483.0 |         0.2 | 2015-11-12 16:41:16 | 2015-11-12 16:42:34 |   2 |
| SHOW ENGINE INNODB STATUS                                        |      1912.4 |      1912.4 |         0.0 | 2015-11-12 16:37:19 | 2015-11-12 17:07:36 | 687 |
| SHOW GLOBAL VARIABLES                                            |      1091.1 |      1091.1 |        68.8 | 2015-11-12 16:37:19 | 2015-11-12 17:07:36 | 687 |
| SHOW GLOBAL STATUS                                               |       638.7 |       638.7 |        40.8 | 2015-11-12 16:37:19 | 2015-11-12 17:07:36 | 687 |
| SELECT LEFT ( `digest_text` , ? ) , SUM ( `timer_end` - `timer_s |       356.2 |       356.2 |        42.4 | 2015-11-12 16:42:38 | 2015-11-12 16:45:00 |   6 |
| SELECT `digest_text` , SUM ( `timer_end` - `timer_start` ) / ? A |       325.3 |       325.3 |         0.4 | 2015-11-12 16:40:44 | 2015-11-12 16:42:18 |   3 |
| SELECT `DIGEST_TEXT` , ( `TIMER_END` - `TIMER_START` ) / ? AS `e |       163.2 |       163.2 |         1.0 | 2015-11-12 16:37:44 | 2015-11-12 16:39:22 |   9 |
| SELECT LOWER ( REPLACE ( trx_state , ?, ... ) ) AS state , COUNT |       133.9 |       133.9 |        80.2 | 2015-11-12 16:37:19 | 2015-11-12 17:07:36 | 687 |
+------------------------------------------------------------------+-------------+-------------+-------------+---------------------+---------------------+-----+

TABLES NEVER WRITTEN TO

If you want to find tables which it was never written to (or read from) since last instance restart you can use the following query. Works since MySQL 5.6

Caution:

• count_read can only be taken as argument if a physical backup method (NOT mysqldump) is used.
• If count_write is 0 it does not necessarily mean that there was no write statement (no matching write)!
• If tables are empty SELECT statements are not counted (count_read = 0).

SELECT t.table_schema, t.table_name, t.table_rows, tio.count_read, tio.count_write
  FROM information_schema.tables AS t
  JOIN performance_schema.table_io_waits_summary_by_table AS tio
    ON tio.object_schema = t.table_schema AND tio.object_name = t.table_name
 WHERE t.table_schema NOT IN ('mysql', 'information_schema', 'performance_schema', 'sys')
   AND tio.count_write = 0
 ORDER BY t.table_schema, t.table_name
;
http://www.fromdual.com/mysql-performance-schema-hints