Mysql Performance Schema - fossasia 2016
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This document discusses the MySQL Performance Schema, which provides visibility into the internal workings of the MySQL server. It describes the need for the Performance Schema, its design including instruments and statistics tables. It then covers some use cases for analyzing statement performance and troubleshooting issues like long running queries or stuck sessions. Finally, it outlines some new features introduced in MySQL 5.7 like additional instruments and tables to gain more insights.
Mysql Performance Schema - fossasia 2016
- 1. Copyright © 2016, Oracle and/or its affiliates. All rights reserved. | MySQL Performance Schema A great insight of MySQL server execution Mayank Prasad Principal Member Technical Staff Oracle, MySQL March 20, 2016 Copyright © 2014, Oracle and/or its affiliates. All rights reserved. |
- 2. Copyright © 2016, Oracle and/or its affiliates. All rights reserved. | Safe Harbor Statement The following is intended to outline our general product direction. It is intended for information purposes only, and may not be incorporated into any contract. It is not a commitment to deliver any material, code, or functionality, and should not be relied upon in making purchasing decisions. The development, release, and timing of any features or functionality described for Oracle’s products remains at the sole discretion of Oracle. 2
- 3. Copyright © 2016, Oracle and/or its affiliates. All rights reserved. | Program Agenda Need and Design Instruments and instrumentation Statistics tables Use cases What’s new in MySQL 5.7 1 2 3 4 5 3
- 4. Copyright © 2016, Oracle and/or its affiliates. All rights reserved. | Program Agenda Need and Design Instruments and instrumentation Statistics tables Use cases What’s new in MySQL 5.7 1 2 3 4 5 4
- 5. Copyright © 2016, Oracle and/or its affiliates. All rights reserved. | Why Performance Schema? ? 5 Session stuck? Hot table? Code contention? Slow application? Too much disk spin? Low throughput? High traffic on link? End User MySQL Developer Application Developer DBA Storage Network System
- 6. Copyright © 2016, Oracle and/or its affiliates. All rights reserved. | What it is? “Performance Schema is a mechanism to give user an insight of what is happening behind the scene when MySQL server is running.” • Introduced in MySQL 5.5 • New storage engine : Performance Schema • New Database : performance_schema • Statistics stored in tables (hard coded DDLs). • Non persistent data • SQL user interface 6
- 7. Copyright © 2016, Oracle and/or its affiliates. All rights reserved. | MySQL 5.7 Performance Schema : Design Block Diagram MySQL Server Instrumentation points (P_S hooks) P_S Internal Buffers P_S Storage Engine Storage Engine Interface Statistics Report Fetch Data SQL Query Collect Data Store Data P_S Tables 7
- 8. Copyright © 2016, Oracle and/or its affiliates. All rights reserved. | Program Agenda Need and Design Instruments and instrumentation Statistics tables Use cases What’s new in MySQL 5.7 1 2 3 4 5 8
- 9. Copyright © 2016, Oracle and/or its affiliates. All rights reserved. | Instruments 9 • 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 performance_schema.setup_instruments table. wait/io/file/myisam/log statement/sql/select
- 10. Copyright © 2016, Oracle and/or its affiliates. All rights reserved. | Instruments contd… Table setup_instruments 10 SETUP_INSTRUMENTS NAME ENABLED TIMED statement/sql/select YES YES statement/sql/create_table YES NO statement/com/Create DB NO NO … … stage/sql/closing tables NO NO stage/sql/Opening tables NO NO stage/sql/optimizing YES YES
- 11. Copyright © 2016, Oracle and/or its affiliates. All rights reserved. | Program Agenda Need and Design Instruments and instrumentation Statistics tables Use cases What’s new in MySQL 5.7 1 2 3 4 5 11
- 12. Copyright © 2016, Oracle and/or its affiliates. All rights reserved. | Statistics Tables in Performance Schema 12 SETUP TABLES Instruments Actors Objects Consumers TIMERS EVENTS TABLES Transactions Statements Stages Waits Idle REPLICATION SUMMARY SYSTEM VARIABLES STATUS VARIABLES LOCK TABLES Metadata locks Table Handles SUMMARY TABLES Events Memory File I/O, Table I/O, Table locks Socket Connection … CONNECTION Attribute Type INSTANCE TABLES Mutex RW_locks File Sockets Cond MISC By_global By_thread By_user/host By_account By_digest
- 13. Copyright © 2016, Oracle and/or its affiliates. All rights reserved. | Program Agenda Need and Design Instruments and instrumentation Statistics tables Use cases What’s new in MySQL 5.7 1 2 3 4 5 13
- 14. Copyright © 2016, Oracle and/or its affiliates. All rights reserved. | What does Performance Schema provide … update performance_schema.setup_instruments set ENABLED='YES', TIMED='YES'; 14 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; Two insertsThree inserts Latest Statement
- 15. Copyright © 2016, Oracle and/or its affiliates. All rights reserved. | 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 15 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
- 16. Copyright © 2016, Oracle and/or its affiliates. All rights reserved. | What does Performance Schema provide … (cont.) Statements Statistics (cont.) * Timer unit is PICOSECOND. 16 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 … … …
- 17. Copyright © 2016, Oracle and/or its affiliates. All rights reserved. | Use case 1 Problem statement 17 • 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 ? …
- 18. Copyright © 2016, Oracle and/or its affiliates. All rights reserved. | Use case 1 Diagnosis 18 – 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’;
- 19. Copyright © 2016, Oracle and/or its affiliates. All rights reserved. | Use case 2 Statements giving errors ( or warnings) 19 SELECT DIGEST_TEXT, SCHEMA_NAME, COUNT_STAR, SUM_ERRORS, SUM_WARNINGS FROM performance_schema.events_statements_summary_by_digest WHERE SUM_ERRORS > 0 ORDER BY SUM_ERRORS DESC limit 1G; 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
- 20. Copyright © 2016, Oracle and/or its affiliates. All rights reserved. | Use case 3 Problem Statement 20 • Multithreaded environment • My session is stuck • No idea why • What to do ? …
- 21. Copyright © 2016, Oracle and/or its affiliates. All rights reserved. | 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 21 SELECT * FROM events_waits_current WHERE THREAD_ID = T1;
- 22. Copyright © 2016, Oracle and/or its affiliates. All rights reserved. | Event Hierarchy Session Transaction *Statement Stage Wait sync, lock, i/o * Statements for non-transactions tables are not part of Transaction instrumentation. 22
- 23. Copyright © 2016, Oracle and/or its affiliates. All rights reserved. | Event Hierarchy 23 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
- 24. Copyright © 2016, Oracle and/or its affiliates. All rights reserved. | Instruments available Monitored activities 24 • Instrumentation for – I/O operation (file, table, NET) – Locking (mutex, r/w locks, table locks, MDLs) – EVENT (transactions, statements, stages, waits, idle) – Stored Programs (Procedures, Functions, Triggers, Events) – User/host/account – Memory – And many more …
- 25. Copyright © 2016, Oracle and/or its affiliates. All rights reserved. | Program Agenda Need and Design Instruments and instrumentation Statistics tables Use cases What’s new in MySQL 5.7 1 2 3 4 5 25
- 26. Copyright © 2016, Oracle and/or its affiliates. All rights reserved. | 26 What’s new in MySQL 5.7 2626 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 Reduced memory foot print MySQL 5.7 Global/Session variables/status 87 Tables and 1000+ Instruments …
- 27. Copyright © 2016, Oracle and/or its affiliates. All rights reserved. | SYS Schema (earlier known as P_S Helper) What’s new in MySQL 5.7 Procedures Functions Views
- 28. Copyright © 2016, Oracle and/or its affiliates. All rights reserved. | Thank You! Q&A ? Copyright © 2014, Oracle and/or its affiliates. All rights reserved. |
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