MySQL Performance Schema in Action: the Complete Tutorial

MySQL Performance Schema
in Action
November, 5, 2018
Sveta Smirnova, Alexander Rubin with Nickolay Ihalainen

•Internal Diagnostic in MySQL
•Conﬁguration
•5.6+: Statements Instrumentation
•5.7+: Prepared Statements
•5.7+: Stored Routines
•5.7+: Locks Diagnostic
•5.7+: Memory Usage
•5.7+: Replication
•5.7+: Variables
•8.0+: Errors Summary
Table of Contents
2

• MySQL Support engineer
• Author of
• MySQL Troubleshooting
• JSON UDF functions
• FILTER clause for MySQL
• Speaker
• Percona Live, OOW, Fosdem,
DevConf, HighLoad...
Who We Are: Sveta Smirnova
4

• Principal Consultant in
Architecture & Projects
• With MySQL for > 12 years
• Speaker
• Percona Live, OOW,
HighLoad...
Who We Are: Alexander Rubin
5

• Senior Support Engineer
• In Percona for 7+ years
• DBA Expert in
• MySQL
• MongoDB
• PostgreSQL
Who We Are: Nickolay Ihalainen
6

• INFORMATION SCHEMA
• SHOW commands
• Metadata
• Storage engine extentions
Runtime
Can be anything
Old Style
8

• SHOW commands
• Status variables
• Runtime
Old Style
8

• SHOW commands
• Administration statements
• ANALYZE
• EXPLAIN
• CHECK
Old Style
8

• SHOW commands
• Administration statements
• No or limited information on
• Performance
• Internal server operations
Old Style
8

• Introduced in version 5.5
Performance Schema
9

• Runtime performances statistics
Performance Schema
9

• Runtime performances statistics
• Wraps the diagnosed code
locker = PSI_RWLOCK_CALL(start_rwlock_wrwait)(
&state, lock->pfs_psi, PSI_RWLOCK_TRYEXCLUSIVELOCK,
file_name, static_cast<uint>(line));
ret = rw_lock_x_lock_func_nowait(lock, file_name, line);
if (locker != NULL)
PSI_RWLOCK_CALL(end_rwlock_wrwait)(
locker, static_cast<int>(ret));
Performance Schema
9

How Does Performance Schema Works?
10

• Must be supported by the component
• Collects data only after they are enabled
• Never frees allocated memory
Performance Schema Limitations
13

• Views on Performance Schema tables
• Stored routines
sys Schema
14

• Stored routines
• Easier conﬁguration
• Shortcuts to typical use cases
sys Schema
14

• Stored routines
• Easier conﬁguration
• Shortcuts to typical use cases
• 5.7+: Installed by default
• Before: github.com/mysql/mysql-sys
sys Schema
14

• Statements
• Locks
• Memory Usage
• Replication
• Variables
• Errors
What will We Discuss Today?
15

5.6
• 52 tables
• 561 instrs
589 Percona Server
• 31 variables
5.7
• 87 tables
• 1029 instrs
1067 Percona Server
• 42 variables
8.0
• 102 tables
• 1202 instrs
1229 Percona Server
• 44 variables
What is Inside?
17

• Defaults
• ON
5.7: Only global, thread, statements and
transactions instrumentation
8.0: Memory and MDL
Performance Schema Defaults
18

• Defaults
• ON
5.7: Only global, thread, statements and
transactions instrumentation
8.0: Memory and MDL
• All other instruments/consumers disabled
Performance Schema Defaults
18

• We will turn required instrumentation ON
for each exercise separately
Prepare
19

• We will use pattern
update performance_schema.setup_consumers set enabled=’yes’
where name like ’OUR_REQUIREMENT_%’;
update performance_schema.setup_instruments set enabled=’yes’, timed=’yes’
where name like ’OUR_REQUIREMENT_%’;
Prepare
19

• Or easier
call sys.ps_setup_enable_consumer(YOUR_CONSUMER);
call sys.ps_setup_enable_instrument(YOUR_INSTRUMENT);
Prepare
19

• Be careful!
• They are memory and CPU intensive
• Do not turn them all ON until needed
Prepare
19

5.6+: Statements Instrumentation

• Why statements are slow?
• Examine more rows than return/change
• Use disk instead of memory
• Full table scan instead of index
• This is not full list!
What Can We Discover?
22

• Why statements are slow?
• Performance Schema has
• Per-query statistics
• Most evolving stages
What Can We Discover?
22

• events statements * and
prepared statements instances tables
• Important ﬁeld names
CREATED TMP DISK TABLES
CREATED TMP TABLES
SELECT FULL JOIN
SELECT RANGE CHECK
SELECT SCAN
SORT MERGE PASSES
SORT SCAN
Why Statements are Slow?
23

• Views in sys schema
• Important view names
statement analysis
statements with full table scans
statements with runtimes in 95th percentile
statements with sorting
statements with temp tables
statements with errors or warnings
23

• Digest tables
• Combined statistics
events statements summary by account by event name
events statements summary by host by event name
events statements summary by thread by event name
events statements summary by user by event name
events statements summary global by event name
5.7+: events statements summary by program
23

• Digest tables
• Histogram Summary
events statements histogram by digest
events statements histogram global
Do NOT mix with Optimizer histograms!
23

• Digest tables
• events statements summary by digest
SCHEMA NAME
DIGEST
DIGEST TEXT
8.0+: QUERY SAMPLE TEXT
23

mysql> SELECT THREAD_ID TID, SUBSTR(SQL_TEXT, 1, 50) SQL_TEXT, ROWS_SENT RS,
-> ROWS_EXAMINED RE,CREATED_TMP_TABLES,NO_INDEX_USED,NO_GOOD_INDEX_USED
-> FROM performance_schema.events_statements_history
-> WHERE NO_INDEX_USED=1 OR NO_GOOD_INDEX_USED=1G
********************** 1. row **********************
TID: 10124
SQL_TEXT: select emp_no, first_name, last_name from employee
RS: 97750
RE: 397774
CREATED_TMP_TABLES: 0
NO_INDEX_USED: 1
NO_GOOD_INDEX_USED: 0
...
Which Queries Do Not Use Indexes?
24

mysql> SELECT query, total_latency, no_index_used_count, rows_sent,
-> rows_examined
-> FROM sys.statements_with_full_table_scans
-> WHERE db=’employees’ AND query NOT LIKE ’%performance_schema%’G
********************** 1. row **********************
query: SELECT COUNT ( ‘emp_no‘ ) FROM ... ‘emp_no‘ )
WHERE ‘title‘ = ?
total_latency: 805.37 ms
no_index_used_count: 1
rows_sent: 1
rows_examined: 397774
...
Take it Easy: Index Usage with sys Schema
25

mysql> select DIGEST, DIGEST_TEXT, COUNT_STAR, SUM_CREATED_TMP_DISK_TABLES,
-> SUM_SELECT_FULL_JOIN, SUM_SELECT_RANGE , SUM_SELECT_SCAN , SUM_NO_INDEX_USED,
-> SUM_ROWS_SENT, SUM_ROWS_EXAMINED
-> from events_statements_summary_by_digest where SUM_NO_INDEX_USED > 0G
*************************** 1. row ***************************
DIGEST: 3884185b07312b354c4918f2368d8fe2c431aeb8e39bf8ff5c3dcc6
DIGEST_TEXT: SELECT ‘c‘ FROM ‘sbtest1‘ WHERE ‘id‘ BETWEEN ? AND ?
COUNT_STAR: 1501791
SUM_CREATED_TMP_DISK_TABLES: 0
SUM_SELECT_FULL_JOIN: 0
SUM_SELECT_RANGE: 1501840
SUM_SELECT_SCAN: 4
SUM_NO_INDEX_USED: 4
SUM_ROWS_SENT: 150872400
SUM_ROWS_EXAMINED: 152872000
...
Take it Easy: with Digest Tables
26

• Login into EC2 instance
• Login: see your card
• Password: see your card
Statements: practice
27

• Start the task
27

• Inside MySQL client
CALL help_task()G
CALL help_solve()G
• We need to ﬁnd slowest queries:
• With largest response time
• With large scanned rows number
• Not using indexes
• Creating temporary tables
27

• events stages * tables
Statements Deep Dive
28

• Same information as in table
INFORMATION SCHEMA.PROCESSLIST or
SHOW PROCESSLIST output
• init
• executing
• Opening tables
28

• init
• executing
• Opening tables
• Replacement for SHOW PROFILE
28

• init
• executing
• Opening tables
• Replacement for SHOW PROFILE
• Only server-level
• No storage engine information!
28

• Instruments
mysql> select name from setup_instruments where name like ’stage%’;
+--------------------------------------------------------------------------
| name
+--------------------------------------------------------------------------
| stage/sql/After create
| stage/sql/allocating local table
| stage/sql/preparing for alter table
| stage/sql/altering table
| stage/sql/committing alter table to storage engine
| stage/sql/Changing master
| stage/sql/Checking master version
...
• Enable those you want to examine
Stages: conﬁguration
29

• Everything, related to temporary tables
• EVENT NAME LIKE ’stage/sql/%tmp%’
• Everything, related to locks
• EVENT NAME LIKE ’stage/sql/%lock%’
• Everything in state ”Waiting for”
• EVENT NAME LIKE ’stage/%/Waiting for%’
• Frequently met issues
Stages Shortcuts
30

• Everything, related to temporary tables
• Everything, related to locks
• Everything in state ”Waiting for”
• Frequently met issues
• EVENT NAME=’stage/sql/freeing items’
• EVENT NAME=’stage/sql/Sending data’
• EVENT NAME=’stage/sql/cleaning up’
• EVENT NAME=’stage/sql/closing tables’
• EVENT NAME=’stage/sql/end’
Stages Shortcuts
30

mysql> SELECT eshl.event_name, sql_text, eshl.timer_wait/1000000000000 w_s
-> FROM performance_schema.events_stages_history_long eshl
-> JOIN performance_schema.events_statements_history_long esthl
-> ON (eshl.nesting_event_id = esthl.event_id)
-> WHERE eshl.timer_wait > 1*10000000000G
*************************** 1. row ***************************
event_name: stage/sql/Sending data
sql_text: SELECT COUNT(emp_no) FROM employees JOIN salaries USING(emp_no)
WHERE hire_date=from_date
w_s: 0.8170
1 row in set (0.00 sec)
Stages Example: Which Stage Run Critically Long?
31

• Contains current prepared statements
Table prepared statements instances
33

• Contains current prepared statements
• Statistics by
• Which thread owns the statement
• How many times executed
• Optimizer statistics, similar to
events statements *
Table prepared statements instances
33

• Instruments
statement/sql/prepare_sql
statement/sql/execute_sql
statement/com/Prepare
statement/com/Execute
Prepared Statements: conﬁguration
34

• Instruments
• Consumers
• prepared statements instances
34

• Instruments
• Consumers
• Size
mysql> select @@performance_schema_max_prepared_statements_instancesG
*************************** 1. row ***************************
@@performance_schema_max_prepared_statements_instances: -1
34

mysql1> prepare stmt from ’select count(*) from employees where hire_date > ?’;
Query OK, 0 rows affected (0.00 sec)
Statement prepared
mysql1> set @hd=’1995-01-01’;
mysql1> execute stmt using @hd;
+----------+
| count(*) |
+----------+
| 34004 |
+----------+
Example: Prepared Statement
35

mysql1> prepare stmt from ’select count(*) from employees where hire_date > ?’;
Statement prepared
mysql1> set @hd=’1995-01-01’;
mysql1> execute stmt using @hd;
+----------+
| count(*) |
+----------+
| 34004 |
+----------+
• Try EXECUTE with different values
Example: Prepared Statement
35

mysql2> select statement_name, sql_text, owner_thread_id, count_reprepare,
-> count_execute, sum_timer_execute from prepared_statements_instancesG
*************************** 1. row ***************************
statement_name: stmt
sql_text: select count(*) from employees where hire_date > ?
owner_thread_id: 22
count_reprepare: 0
count_execute: 3
sum_timer_execute: 4156561368000
mysql1> drop prepare stmt;
mysql2> select * from prepared_statements_instancesG
Empty set (0.00 sec)
Example: diagnosis
36

• Start the task
Prepared Statements: practice
37

CALL help_task()G
CALL help_solve()G
• We need to ﬁnd out how effective is the
prepared statement
Prepared Statements: practice
37

mysql> select * from setup_instruments where name like ’statement/sp%’;
+--------------------------------+---------+-------+
| NAME | ENABLED | TIMED |
+--------------------------------+---------+-------+ ...
| statement/sp/stmt | YES | YES | | statement/sp/hreturn |
| statement/sp/set | YES | YES | | statement/sp/cpush |
| statement/sp/set_trigger_field | YES | YES | | statement/sp/cpop |
| statement/sp/jump | YES | YES | | statement/sp/copen |
| statement/sp/jump_if_not | YES | YES | | statement/sp/cclose |
| statement/sp/freturn | YES | YES | | statement/sp/cfetch |
| statement/sp/hpush_jump | YES | YES | | statement/sp/error |
| statement/sp/hpop | YES | YES | | statement/sp/set_case_expr |
... +----------------------------+
New Instruments
39

• What happens inside the routine
Stored Routines Instrumentation
40

• What happens inside the routine
• Queries, called from the routine
• statement/sp/stmt
Stored Routines Instrumentation
40

• We will use this procedure
CREATE DEFINER=‘root‘@‘localhost‘ PROCEDURE ‘sp_test‘(val int)
BEGIN
DECLARE CONTINUE HANDLER FOR 1364, 1048, 1366
BEGIN
INSERT IGNORE INTO t1 VALUES(’Some string’);
GET STACKED DIAGNOSTICS CONDITION 1 @stacked_state = RETURNED_SQLSTATE;
GET STACKED DIAGNOSTICS CONDITION 1 @stacked_msg = MESSAGE_TEXT;
END;
INSERT INTO t1 VALUES(val);
END
Stored Routines: example
41

• We will use this procedure
CREATE DEFINER=‘root‘@‘localhost‘ PROCEDURE ‘sp_test‘(val int)
BEGIN
DECLARE CONTINUE HANDLER FOR 1364, 1048, 1366
BEGIN
INSERT IGNORE INTO t1 VALUES(’Some string’);
GET STACKED DIAGNOSTICS CONDITION 1 @stacked_state = RETURNED_SQLSTATE;
GET STACKED DIAGNOSTICS CONDITION 1 @stacked_msg = MESSAGE_TEXT;
END;
INSERT INTO t1 VALUES(val);
END
• When HANDLER called?
Stored Routines: example
41

• Start the task
Stored Routines: practice
44

CALL help_task()G
CALL help_solve()G
CALL task_prepare();
• We need to ﬁnd out why procedure takes
different time each run
• For better output set pager to less:
mysql> P less
Stored Routines: practice
44

• Table METADATA LOCKS
5.7+: MDL
46

• Which thread is waiting for a lock
5.7+: MDL
46

• Which thread holds the lock
5.7+: MDL
46

• Which thread holds the lock
• Not only for tables:
GLOBAL, SCHEMA, TABLE, FUNCTION, PROCEDURE, EVENT, COMMIT, USER LEVEL
LOCK, TABLESPACE
5.7+: MDL
46

• Instruments
• wait/lock/metadata/sql/mdl
MDL: conﬁguration
47

• Instruments
• Consumers
• METADATA LOCKS
MDL: conﬁguration
47

mysql> select processlist_id, object_type, lock_type, lock_status, source
-> from metadata_locks join threads on (owner_thread_id=thread_id)
-> where object_schema=’employees’ and object_name=’titles’G
*************************** 1. row ***************************
processlist_id: 4
object_type: TABLE
lock_type: EXCLUSIVE
lock_status: PENDING -- waits
source: mdl.cc:3263
*************************** 2. row ***************************
processlist_id: 5
object_type: TABLE
lock_type: SHARED_READ
lock_status: GRANTED -- holds
source: sql_parse.cc:5707
METADATA LOCKS: example
48

• Start the task
MDL: practice
49

CALL help_task()G
CALL help_solve()G
• We need to ﬁnd out what prevents ALTER
from ﬁnishing
MDL: practice
49

• Information about locks, held by engine
8.0.+: Data Locks
50

• Only for engines with own locking models
8.0.+: Data Locks
50

• Currently only InnoDB
8.0.+: Data Locks
50

• Currently only InnoDB
• Replacement for I S tables
• INNODB LOCKS
• INNODB LOCK WAITS
8.0.+: Data Locks
50

Unlike most Performance Schema data collection, there are no instruments
for controlling whether data lock information is collected or system variables for
controlling data lock table sizes. The Performance Schema collects information
that is already available in the server, so there is no memory or CPU overhead
to generate this information or need for parameters that control its collection.
https://dev.mysql.com/doc/refman/8.0/en/data-locks-table.html
Data Locks: conﬁguration
51

• Which lock is held
*************************** 4. row ***************************
ENGINE: INNODB
ENGINE_LOCK_ID: 2408:0:393:2
ENGINE_TRANSACTION_ID: 2408
THREAD_ID: 34
OBJECT_SCHEMA: test
OBJECT_NAME: t
INDEX_NAME: PRIMARY
LOCK_TYPE: RECORD
LOCK_MODE: X
LOCK_STATUS: GRANTED
LOCK_DATA: 12345
Table DATA LOCKS
52

• Which lock is requested
*************************** 2. row ***************************
ENGINE: INNODB
ENGINE_LOCK_ID: 2409:0:393:2
ENGINE_TRANSACTION_ID: 2409
THREAD_ID: 36
OBJECT_SCHEMA: test
OBJECT_NAME: t
INDEX_NAME: PRIMARY
LOCK_TYPE: RECORD
LOCK_MODE: X
LOCK_STATUS: WAITING
LOCK_DATA: 12345
Table DATA LOCKS
52

• Which lock is requested
• Both record-level and table level
p_s> select * from data_locksG
*************************** 1. row ***************************
...
LOCK_TYPE: TABLE
LOCK_MODE: IX
LOCK_STATUS: GRANTED
LOCK_DATA: NULL
*************************** 2. row ***************************
...
LOCK_TYPE: RECORD
Table DATA LOCKS
52

• Maps lock waits with granted locks
Table DATA LOCK WAITS
53

• Maps lock waits with granted locks
• Only granted blocking other transactions
p_s> select ENGINE, ... from data_lock_waitsG
*************************** 1. row ***************************
ENGINE: INNODB
REQUESTING_ENGINE_LOCK_ID: 2409:0:393:2
REQUESTING_ENGINE_TRANSACTION_ID: 2409
REQUESTING_THREAD_ID: 36
BLOCKING_ENGINE_LOCK_ID: 2408:0:393:2
BLOCKING_ENGINE_TRANSACTION_ID: 2408
BLOCKING_THREAD_ID: 34
1 row in set (0,01 sec)
Table DATA LOCK WAITS
53

• Partition
• Subpartition
• Lock data
• Requesting and blocking thread id
New Information
54

• View innodb lock waits
In sys Schema
55

• Takes additional information from
INFORMATION SCHEMA.INNODB TRX
In sys Schema
55

sys> select locked_table, ...
-> from innodb_lock_waitsG
*************************** 1. row ***************************
locked_table: ‘test‘.‘t‘ blocking_pid: 4
locked_index: PRIMARY blocking_query: NULL
locked_type: RECORD blocking_trx_rows_locked: 1
waiting_trx_rows_locked: 1 blocking_trx_rows_modified: 1
waiting_trx_rows_modified: 0 sql_kill_blocking_query: KILL QUERY 4
waiting_pid: 6 sql_kill_blocking_connection: KILL 4
waiting_query: UPDATE t SET f=’bar’ WHERE id=12345
In sys Schema
55

• Start the task
Data Locks: Practice
56

CALL help_task()G
CALL help_solve()G
• We need to ﬁnd
• Which transaction holds the lock
• What is the missed statement
• Which row is locked
• Which partition is locked
Data Locks: Practice
56

• Instruments
• Consumers
• Digest tables in Performance Schema
Memory: conﬁguration
58

• Memory, used by internal mysqld structures
Memory Diagnostic
59

• Aggregated by
• Global
• Thread
• Account
• Host
• User
Memory Diagnostic
59

• Aggregated by
• Global
• Thread
• Account
• Host
• User
• Nice views in sys schema
Memory Diagnostic
59

mysql> select thread_id tid, user, current_allocated ca, total_allocated
-> from sys.memory_by_thread_by_current_bytes;
+-----+-------------------------+-------------+-----------------+
| tid | user | ca | total_allocated |
+-----+-------------------------+-------------+-----------------+
| 1 | sql/main | 2.53 GiB | 2.69 GiB |
| 150 | root@127.0.0.1 | 4.06 MiB | 32.17 MiB |
| 146 | sql/slave_sql | 1.31 MiB | 1.44 MiB |
| 145 | sql/slave_io | 1.08 MiB | 2.79 MiB |
...
| 60 | innodb/io_read_thread | 0 bytes | 384 bytes |
| 139 | innodb/srv_purge_thread | -328 bytes | 754.21 KiB |
| 69 | innodb/io_write_thread | -1008 bytes | 34.28 KiB |
| 4 | innodb/io_log_thread | -2880 bytes | 132.38 KiB |
Memory Usage by Thread
60

mysql> select * from sys.memory_by_thread_by_current_bytes
-> order by current_allocated descG
*************************** 1. row ***************************
thread_id: 152
user: lj@127.0.0.1
current_count_used: 325
current_allocated: 36.00 GiB
current_avg_alloc: 113.43 MiB
current_max_alloc: 36.00 GiB
total_allocated: 37.95 GiB
...
• Find threads, eating memory, in a second!
Threads Statistics
61

• memory summary by account by event name
• memory summary by host by event name
• memory summary by thread by event name
• memory summary by user by event name
• memory summary global by event name
RAW Performance Schema tables
62

• You must enable memory instrumentation!
62

• You must enable memory instrumentation!
• sys schema includes user name
62

• NAME@HOST - regular user
Users in sys.memory * tables
63

• System users
• sql/main
• innodb/*
• ...
63

• System users
• sql/main
• innodb/*
• ...
• Data comes from table THREADS
63

• Start the task
Memory Usage: practice
64

CALL help_task()G
CALL help_solve()G
• We need to ﬁnd out how much memory
uses SysBench load, running in parallel
• To identify how much RAM used by whole
server run
select * from sys.memory_global_total;
Memory Usage: practice
64

• Data from SHOW SLAVE STATUS available in
replication * tables
Major Improvements
66

• Support of Replication Channels
(Multi-master slave)
Major Improvements
66

• Support of Replication Channels
(Multi-master slave)
• More instruments for GTID
Major Improvements
66

• No need to parse SHOW output
SLAVE STATUS
67

• Conﬁguration
• replication connection configuration
• replication applier configuration
SLAVE STATUS
67

• Conﬁguration
• IO thread
• replication connection status
SLAVE STATUS
67

• Conﬁguration
• IO thread
• SQL thread
• replication applier status
• replication applier status by coordinator - MTS only
• replication applier status by worker
• replication applier global filters
• replication applier filters
SLAVE STATUS
67

• Conﬁguration
• IO thread
• SQL thread
• Group replication
• replication group members
• replication group member stats
SLAVE STATUS
67

• Conﬁguration
mysql> select * from replication_connection_configuration
-> join replication_applier_configuration using(channel_name)G
*************************** 1. row ***************************
CHANNEL_NAME:
HOST: 127.0.0.1
PORT: 13000
USER: root
NETWORK_INTERFACE:
AUTO_POSITION: 1
SSL_ALLOWED: NO
SSL_CA_FILE:
...
CHANNEL_NAME:
DESIRED_DELAY: 0
SLAVE STATUS
68

• State of IO Thread
mysql> select * from replication_connection_statusG
*************************** 1. row ***************************
CHANNEL_NAME:
GROUP_NAME:
SOURCE_UUID: d0753e78-14ec-11e5-b3fb-28b2bd7442fd
THREAD_ID: 21
SERVICE_STATE: ON
COUNT_RECEIVED_HEARTBEATS: 17
LAST_HEARTBEAT_TIMESTAMP: 2015-06-17 15:49:08
RECEIVED_TRANSACTION_SET:
LAST_ERROR_NUMBER: 0
LAST_ERROR_MESSAGE:
LAST_ERROR_TIMESTAMP: 0000-00-00 00:00:00
SLAVE STATUS
69

• Coordinator thread for multiple workers
mysql> select * from replication_applier_status join
-> replication_applier_status_by_coordinator using(channel_name)G
*************************** 1. row ***************************
CHANNEL_NAME:
SERVICE_STATE: ON
REMAINING_DELAY: NULL
COUNT_TRANSACTIONS_RETRIES: 0
THREAD_ID: 76
SERVICE_STATE: ON
LAST_ERROR_MESSAGE:
LAST_ERROR_TIMESTAMP: 0000-00-00 00:00:00.000000
LAST_PROCESSED_TRANSACTION: c634ce2d-cbb3-11e8-9532-0242cedce297:6
LAST_PROCESSED_TRANSACTION_ORIGINAL_COMMIT_TIMESTAMP: 2018-10-09 14:59:05.281818
Performance Schema: State of SQL Thread
70

• Multi-source slave
mysql> select * from replication_applier_status join
-> replication_applier_status_by_worker using(channel_name)G
*************************** 1. row ***************************
CHANNEL_NAME: master-01
SERVICE_STATE: ON
REMAINING_DELAY: NULL
...
LAST_APPLIED_TRANSACTION: c634ce2d-cbb3-11e8-9532-0242cedce297:7
LAST_APPLIED_TRANSACTION_ORIGINAL_COMMIT_TIMESTAMP: 2018-10-09 15:12:56.285995
...
70

• Multi-source slave
*************************** 2. row ***************************
CHANNEL_NAME: m-03
SERVICE_STATE: OFF
...
LAST_ERROR_MESSAGE: Worker 1 failed executing transaction ...
LAST_ERROR_TIMESTAMP: 2018-10-09 15:15:14.306672
LAST_APPLIED_TRANSACTION: c63ae70c-cbb3-11e8-b634-0242cedce297:2
...
LAST_APPLIED_TRANSACTION_END_APPLY_TIMESTAMP: 2018-10-09 15:13:33.770744
APPLYING_TRANSACTION: c63ae70c-cbb3-11e8-b634-0242cedce297:3
...
70

• RECEIVED TRANSACTION SET
in table replication connection status
GTID Diagnostics
71

• RECEIVED TRANSACTION SET
in table replication connection status
• LAST SEEN TRANSACTION
in replication applier status by worker
GTID Diagnostics
71

• Single-threaded slave
mysql> select cs.CHANNEL_NAME, cs.SOURCE_UUID, cs.RECEIVED_TRANSACTION_SET,
-> asw.LAST_APPLIED_TRANSACTION, aps.SERVICE_STATE from
-> replication_connection_status cs join replication_applier_status_by_worke
-> asw using(channel_name) join replication_applier_status aps
-> using(channel_name) G
*************************** 1. row ***************************
CHANNEL_NAME:
SOURCE_UUID: 9038967d-7164-11e6-8c88-30b5c2208a0f
RECEIVED_TRANSACTION_SET: 9038967d-7164-11e6-8c88-30b5c2208a0f:1-2
LAST_APPLIED_TRANSACTION: 9038967d-7164-11e6-8c88-30b5c2208a0f:2
SERVICE_STATE: ON
1 row in set (0,00 sec)
GTID: All in One Place
72

• Single-threaded slave
• Multi-threaded
*************************** 1. row ***************************
THREAD_ID: 30
SERVICE_STATE: ON
LAST_APPLIED_TRANSACTION:
...
*************************** 8. row ***************************
THREAD_ID: 37
SERVICE_STATE: ON
LAST_APPLIED_TRANSACTION: 9038967d-7164-11e6-8c88-30b5c2208a0f:3
8 rows in set (0,00 sec)
GTID: All in One Place
72

• Global
mysql> select * from replication_applier_global_filtersG
*************************** 1. row ***************************
FILTER_NAME: REPLICATE_IGNORE_TABLE
FILTER_RULE: test.test
CONFIGURED_BY: CHANGE_REPLICATION_FILTER
ACTIVE_SINCE: 2018-10-09 16:54:45.733490
Replication Filters
73

• Global
• Worker’s
mysql> select * from replication_applier_filtersG
*************************** 1. row ***************************
CHANNEL_NAME: m-01
FILTER_RULE: test.test
CONFIGURED_BY: CHANGE_REPLICATION_FILTER
ACTIVE_SINCE: 2018-10-09 16:54:45.733490
COUNTER: 0
*************************** 2. row ***************************
CHANNEL_NAME: m-03
FILTER_RULE: test.t1
Replication Filters
73

mysql> SELECT * FROM performance_schema.replication_group_membersG
*************************** 1. row ***************************
CHANNEL_NAME: group_replication_applier
MEMBER_ID: c26fc705-cbcc-11e8-b5b8-0242cedce297
MEMBER_HOST: delly
MEMBER_PORT: 24801
MEMBER_STATE: ONLINE
MEMBER_ROLE: PRIMARY
MEMBER_VERSION: 8.0.12
...
Group Replication
74

*************************** 2. row ***************************
MEMBER_ID: f3d2feda-cbcc-11e8-9eb9-0242cedce297
MEMBER_HOST: delly
MEMBER_PORT: 24802
MEMBER_STATE: RECOVERING
MEMBER_ROLE: PRIMARY
MEMBER_VERSION: 8.0.12
Group Replication
74

• replication group member stats
mysql> SELECT * FROM performance_schema.replication_group_member_statsG
*************************** 1. row ***************************
VIEW_ID: 15390963914656312:3
MEMBER_ID: 1dfa4dee-cbcd-11e8-bad1-0242cedce297
COUNT_TRANSACTIONS_IN_QUEUE: 0
COUNT_TRANSACTIONS_CHECKED: 1
COUNT_CONFLICTS_DETECTED: 0
COUNT_TRANSACTIONS_ROWS_VALIDATING: 8
...
Group Replication
74

• Tables in mysql schema
• slave master info
• slave relay log info
• slave worker info
• Join with Performance Schema tables
More Diagnostic
75

• Tables in mysql schema
• slave master info
• slave relay log info
• slave worker info
• Join with Performance Schema tables
• New instruments
• memory
• wait
• stage
More Diagnostic
75

• Not only replication
mysql> select * from log_statusG
*************************** 1. row ***************************
SERVER_UUID: c634ce2c-cbb3-11e8-8900-0242cedce297
LOCAL: {"gtid_executed": "c634ce2d-cbb3-11e8-9532-0242cedce297:1-2",
"binary_log_file": "binlog.000001",
"binary_log_position": 620}
REPLICATION: {"channels": [{"channel_name": "",
"relay_log_file": "delly-relay-bin.000002",
"relay_log_position": 819,
"relay_master_log_file": "binlog.000001",
"exec_master_log_position": 611}]}
STORAGE_ENGINES: {"InnoDB": {"LSN": 19177930, "LSN_checkpoint": 19177930}}
Table log status
76

• Not only replication
• Currently only InnoDB supported!
Table log status
76

• Start the task
Replication: practice
77

CALL help_task()G
CALL help_solve()G
• To open another terminal: Ctrl+b,c
• Connection commands in another terminal
• Master: m
• Slave: s1
• We need to ﬁnd out why replication is
broken and ﬁx it
Replication: practice
77

• Variables
• global variables
• session variables
• user variables by thread
• variables by thread
Variables Instrumentation
79

• Variables
• global status
• session status
• status by [account|host|thread|user]
79

• Variables
• show compatibility 56 = 0
79

• Same information which is in
• SHOW [GLOBAL] STATUS
• I S.GLOBAL VARIABLES
Deprecated in 5.7
Removed in 8.0.1
• I S.SESSION VARIABLES
Deprecated in 5.7
Removed in 8.0.1
Global and Session Variables
80

• I S.GLOBAL VARIABLES
Deprecated in 5.7
Removed in 8.0.1
• I S.SESSION VARIABLES
Deprecated in 5.7
Removed in 8.0.1
• Helps to watch session variables changes
Global and Session Variables
80

• I S.GLOBAL STATUS
Deprecated in 5.7
Removed in 8.0.1
• I S.SESSION STATUS
Deprecated in 5.7
Removed in 8.0.1
Status Variables
81

mysql> SELECT ss.variable_name, ss.variable_value FROM session_status ss
-> LEFT JOIN global_status gs USING(variable_name)
-> WHERE ss.variable_value != gs.variable_value OR gs.variable_value IS NULL;
+----------------------------+----------------+
| variable_name | variable_value |
+----------------------------+----------------+
| Bytes_sent | 197774 |
| Handler_commit | 0 |
| Handler_external_lock | 44 |
| Handler_read_first | 3 |
| Handler_read_key | 523 |
| Handler_read_next | 0 |
| Handler_read_rnd_next | 7241 |
| Opened_table_definitions | 0 |
...
Status Variables
82

• status by
• account
• host
• thread
• user
Possible to Group
83

• status by
mysql> select * from status_by_thread where variable_name=’Handler_write’;
+-----------+---------------+----------------+
+-----------+---------------+----------------+
| 71 | Handler_write | 94 |
| 83 | Handler_write | 477 | -- Most writes
| 84 | Handler_write | 101 |
+-----------+---------------+----------------+
Possible to Group
83

• Grouped by connection
• Sometimes can help to ﬁnd tricky bugs with
persistent connections
mysql> select * from user_variables_by_thread;
+-----------+---------------+----------------+
+-----------+---------------+----------------+
| 71 | baz | boo |
| 84 | foo | bar |
+-----------+---------------+----------------+
User Variables
84

• VARIABLES INFO
• Source of variable
COMPILED
EXPLICIT
COMMAND LINE
DYNAMIC
• Path of option ﬁle if speciﬁed
• Minimum and maximum values
8.0+: Variables Info
85

• VARIABLES INFO
mysql> select * from variables_info where set_user is not nullG
*************************** 1. row ***************************
VARIABLE_NAME: innodb_file_per_table
VARIABLE_SOURCE: DYNAMIC
VARIABLE_PATH:
MIN_VALUE: 0
MAX_VALUE: 0
SET_TIME: 2018-10-09 22:17:34.638459
SET_USER: root
SET_HOST: localhost
*************************** 2. row ***************************
VARIABLE_NAME: max_allowed_packet
VARIABLE_SOURCE: DYNAMIC
VARIABLE_PATH:
85

• VARIABLES INFO
• Source of variable
COMPILED
EXPLICIT
COMMAND LINE
DYNAMIC
• Path of option ﬁle if speciﬁed
• Minimum and maximum values
• No variable values in this table!
85

• Start the task
Variables: practice
86

CALL help_task()G
CALL help_solve()G
• We need to watch progress of INSERT
command, running by stored routine.
• Note what there is parallel load, caused by
SysBench. We are not interested in its
statistics.
Variables: practice
86

• Traditionally aggregated
• events errors summary by account by error
• events errors summary by host by error
• events errors summary by thread by error
• events errors summary by user by error
• events errors summary global by error
Errors Summary Tables
88

mysql> select * from events_errors_summary_by_account_by_error
-> where SUM_ERROR_RAISED > 100G
*************** 1. row ***************
USER: root
HOST: localhost
ERROR_NUMBER: 1213
ERROR_NAME: ER_LOCK_DEADLOCK
SQL_STATE: 40001
SUM_ERROR_RAISED: 221
SUM_ERROR_HANDLED: 0
FIRST_SEEN: 2016-09-28 01:45:09
LAST_SEEN: 2016-09-28 01:47:02
*************** 2. row ***************
USER: root
HOST: localhost
ERROR_NUMBER: 1287
ERROR_NAME: ER_WARN_DEPRECATED_SYNTAX
SQL_STATE: HY000
SUM_ERROR_RAISED: 279
SUM_ERROR_HANDLED: 0
FIRST_SEEN: 2016-09-27 23:59:49
LAST_SEEN: 2016-09-28 01:47:05
Errors Summary: Which Accounts Raise More
Errors?
89

• Start the task
Errors Summary: practice
90

CALL help_task()G
CALL help_solve()G
• We need to ﬁnd all occasions of statements
with errors
• Get the list all accounts which raised errors
• Get the top 3 error types globally
Errors Summary: practice
90

github.com/svetasmirnova/performance schema tutorial
Practice: Download Code
91

Blog of MySQL developers team
Mark Leith: author of sys schema
Ofﬁcial reference manual
Webinar ”Performance Schema for
MySQL Troubleshooting”
More information
92

http://www.slideshare.net/SvetaSmirnova
https://twitter.com/svetsmirnova
https://github.com/svetasmirnova
https://www.linkedin.com/in/alexanderrubin
Thank you!
94

MySQL Performance Schema in Action: the Complete Tutorial

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