mysql performance schema, open source india, 2015

Copyright © 2015, Oracle and/or its affiliates. All rights reserved. |

MySQL Performance SchemaOut of the Box in MySQL 5.7

Copyright © 2015, Oracle and/or its affiliates. All rights reserved.

Mayank PrasadPrincipal Member Technical StaffOracle, MySQLNovember 20, 2015


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Program Agenda

Need and Design

Instruments and instrumentation

Statistics tables

Use cases

What’s new in MySQL 5.7

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Program Agenda

Need and Design


Statistics tables

Use cases


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Copyright © 2015, Oracle and/or its affiliates. All rights reserved. | 5

Why Performance Schema?

SystemLow throughput?

?

DBAHot table?

NetworkHigh traffic on link?

StorageToo much Disk spin?App Developer

Slow application?

MySQL Developer Code contention?

End User stuck session?


MySQL 5.7 Performance Schema : DesignBlock Diagram

MySQLServer

Instrumentation points(P_S hooks)

P_S Internal Buffers

P_SStorageEngine

StorageEngine

Interface StatisticsReport

FetchData

SQL Query

Statistics Collection Statistics Reporting

Collect DataStoreData

P_STables

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Program Agenda

Need and Design


Statistics tables

Use cases


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Enabled/Disabled

at runtime.

Instruments

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• Name of monitored activity.• Tree like structure. Separated by ‘/’.• Left to right : More generic to more specific.

• 1000+ instruments in MySQL 5.7.• Stored in setup_instruments table.

wait/io/file/myisam/logstatement/sql/select


Program Agenda

Need and Design


Statistics tables

Use cases


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Statistics Tables in Performance Schema

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SETUP TABLES

Instruments

Actors

Objects

Consumers

TIMERS

EVENTS TABLES

Transactions

Statements

Stages

Waits

Idle

REPLICATIONSUMMARY

SYSTEM VARIABLES

STATUS VARIABLES

LOCK TABLES

Metadata locks

Table Handles

SUMMARY TABLES

EventsMemory

File I/O, Table I/O, Table locks

SocketConnection

…

CONNECTIONAttribute

Type

INSTANCETABLES

Mutex

RW_locks

File

Sockets

Cond MISC

By_global By_thread By_user/host By_account By_digest


Program Agenda

Need and Design


Statistics tables

Use cases


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What does Performance Schema provide …update setup_instruments set ENABLED='YES', TIMED='YES';

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Connection 1 (Thread 24)start transaction; insert into test.t1 values('11'); commit; start transaction; insert into test.t1 values('12'); commit;start transaction; insert into test.t1 values('13'); commit;select * from test.t1;

Connection 2 (Thread 25)start transaction; insert into test.t2 values('21'); commit;

start transaction; insert into test.t2 values('22'); commit;

Three inserts

Twoinserts

LatestStatement


What does Performance Schema provide … (cont.)Statements Statistics

* Timer unit is PICOSECOND.

EVENTS_STATEMENTS_CURRENT

THREAD_ID 24 25

EVENT_NAME statement/sql/select

statement/sql/commit

TIMER_WAIT 876585000 15998287000

SQL_TEXT select * from test.t1 commit

ROWS_SENT 3 0

NO_INDEX_USED 0 0

SELECT_SCAN 1 0

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EVENTS_STATEMENTS_SUMMARY_BY_THREAD_BY_EVENT_NAME

THREAD_ID 24 25

EVENT_NAME statement/sql/insert

statement/sql/insert

COUNT_STAR 3 2

SUM_TIMER_WAIT 35181659000 3477432000

SUM_ROWS_AFFECTED 3 2

SUM_SELECT_SCAN 0 0

SUM_NO_INDEX_USED 0 0


What does Performance Schema provide … (cont.)Statements Statistics (cont.)

* Timer unit is PICOSECOND.

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EVENTS_STATEMENTS_SUMMARY_GLOBAL_BY_EVENT_NAME

EVENT_NAME statement/sql/insert statement/sql/commit

COUNT_STAR 5 5

SUM_TIMER_WAIT 38659091000 65812216000

… …

SUM_ROWS_AFFECTED 5 0

… … …


Use case 1Description

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• Multiple queries running for long on MySQL Server• Few long running query (taking lots of time)• No idea which one• No idea why• What to do ? …


Use case 1Diagnosis

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– THREAD_ID: 25– EVENT_ID: 89– EVENT_NAME: statement/sql/select– SQL_TEXT : select bla bla bla…;

• Wait ! There’s more!– SELECT_SCAN : 1– NO_INDEX_USED: 1

• Aha !!

SELECT * FROM events_statements_history WHERE TIMER_WAIT > ‘X’;


Use case 2Statements giving errors ( or warnings)

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SELECT DIGEST_TEXT, SCHEMA_NAME, COUNT_STAR, SUM_ERRORS, SUM_WARNINGS FROM events_statements_summary_by_digest WHERE SUM_ERRORS > 0 ORDER BY SUM_ERRORS DESC limit 1\G;

EVENTS_STATEMENTS_SUMMARY_BY_DIGEST

DIGEST_TEXT CREATE TEMPORARY TABLE IF NOT ... _logs` ( `id` INT8 NOT NULL )!

SCHEMA_NAME mem

COUNT_STAR 1725

SUM_ERRORS 1725

SUM_WARNINGS 0

FIRST_SEEN 2014-05-20 10:42:32

LAST_SEEN 2014-05-21 18:39:22


Use case 3Description

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• Multithreaded environment• My session is stuck• No idea why• What to do ? …


Use case 3• What T1 is waiting for

– Say T1 is waiting for mutex_A (column OBJECT_INSTANCE_BEGIN)

• Lets see who has taken this mutex_A

– Ok, so thread T2 is holding mutex_A (column LOCKED_BY_THREAD_ID)

• Find out what thread t2 is waiting for

• And so on…

SELECT * FROM mutex_instances WHERE OBJECT_INSTANCE_BEGIN = mutex_A;

SELECT * FROM events_waits_current WHERE THREAD_ID = T2;

Diagnosis

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SELECT * FROM events_waits_current WHERE THREAD_ID = T1;


Replication Summary TablesTables for replication statistics

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Replication status

Connection Information Execute Information

Connection Configuration Connection StatusExecute Configuration Execute Status

Coordinator/SQL Thread

Worker Thread

replication_connection_configuration

replication_connection_status

replication_execute_status_by_coordinator

replication_execute_status_by_worker

replication_execute_status

replication_execute_configuration



Table Information

replication_connection_configuration (Host, Port, User etc.)

replication_connection_status (Server UUID, Receiver thread ID, Service State etc.)

replication_execute_configuration (Desired Delay)

replication_execute_status (Remaining Delay)

replication_execute_status_by_coordinator (Thread Id, Service State, Last Error info.)

replication_execute_status_by_worker (WID, WTID, Service State, Last error Info.)

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SHOW SLAVE STATUS (Limitations)

– No logical division of information.

– Lots of information packed together.

– No cherry picking (difficult for automation).

– Difficult to scale (more new fields).

Why Performance Schema Tables?

– Split logically into different tables.

– SQL Interface. Fetch what is required.

– Easier to extend.


Event Hierarchy

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event_id

nesting_event_id

event_id

nesting_event_id

event_id

nesting_event_id

event_id

nesting_event_id

event_id

nesting_event_id

event_id

nesting_event_id

event_id

nesting_event_id

event_id

nesting_event_id

Transactions Statements Stages Waits


Program Agenda

Need and Design


Statistics tables

Use cases


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EnhancementsNew Instruments

transactionsMemory usage

Stored programs

Prepared statements

Metadata locks

Connection type InnoDB

Stages

User variables

Replication summary

tables

History per session

Scalable memory

allocation

Configurable digest size

…

MySQL 5.7

Global/Session variables/status

87 Tables and 1000+ Instruments


SYS Schema (earlier known as P_S Helper)What’s new in MySQL 5.7

Performance Schema tables

Procedures Functions Views

Information Schema tables

Formatted Statistics

SYS SCHEMA

Many of common

day to day use cases

for DBAs debugging

And tuning


Thank You

mysql performance schema, open source india, 2015

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