MySQL Performance Schema, Open Source India, 2015
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This document discusses the MySQL Performance Schema, which provides monitoring of MySQL server execution at a low level. It describes the need for the Performance Schema, its design including instruments and statistics tables, and use cases for analyzing performance issues like long-running queries, statements causing errors, and troubleshooting stuck sessions. The document also outlines what's new in MySQL 5.7 such as additional instruments, memory usage monitoring, and replication summary tables.
MySQL Performance Schema, Open Source India, 2015
- 1. Copyright © 2015, Oracle and/or its affiliates. All rights reserved. | MySQL Performance Schema Out of the Box in MySQL 5.7 Copyright © 2015, Oracle and/or its affiliates. All rights reserved. Mayank Prasad Principal Member Technical Staff Oracle, MySQL November 20, 2015
- 2. Copyright © 2015, 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 © 2015, 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 © 2015, 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 © 2015, Oracle and/or its affiliates. All rights reserved. | Why Performance Schema? System Low throughput? ? 5 DBA Hot table? Network High traffic on link? Storage Too much Disk spin?App Developer Slow application? MySQL Developer Code contention? End User stuck session?
- 6. Copyright © 2015, 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 6
- 7. Copyright © 2015, 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 7
- 8. Copyright © 2015, Oracle and/or its affiliates. All rights reserved. | Instruments 8 • 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/log statement/sql/select
- 9. Copyright © 2015, 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 9
- 10. Copyright © 2015, Oracle and/or its affiliates. All rights reserved. | Statistics Tables in Performance Schema 10 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
- 11. Copyright © 2015, 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 © 2015, Oracle and/or its affiliates. All rights reserved. | What does Performance Schema provide … update setup_instruments set ENABLED='YES', TIMED='YES'; 12 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 Two inserts Latest Statement
- 13. Copyright © 2015, 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 13 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
- 14. Copyright © 2015, Oracle and/or its affiliates. All rights reserved. | What does Performance Schema provide … (cont.) Statements Statistics (cont.) * Timer unit is PICOSECOND. 14 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 … … …
- 15. Copyright © 2015, Oracle and/or its affiliates. All rights reserved. | Use case 1 Description 15 • 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 ? …
- 16. Copyright © 2015, Oracle and/or its affiliates. All rights reserved. | Use case 1 Diagnosis 16 – 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’;
- 17. Copyright © 2015, Oracle and/or its affiliates. All rights reserved. | Use case 2 Statements giving errors ( or warnings) 17 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 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
- 18. Copyright © 2015, Oracle and/or its affiliates. All rights reserved. | Use case 3 Description 18 • Multithreaded environment • My session is stuck • No idea why • What to do ? …
- 19. Copyright © 2015, 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 19 SELECT * FROM events_waits_current WHERE THREAD_ID = T1;
- 20. Copyright © 2015, Oracle and/or its affiliates. All rights reserved. | Replication Summary Tables Tables for replication statistics 20 Replication status Connection Information Execute Information Connection Configuration Connection Status Execute 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
- 21. Copyright © 2015, Oracle and/or its affiliates. All rights reserved. | Replication Summary Tables Tables for replication statistics 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.) 21
- 22. Copyright © 2015, Oracle and/or its affiliates. All rights reserved. | Replication Summary Tables Tables for replication statistics 22 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.
- 23. Copyright © 2015, 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 © 2015, 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 24
- 25. Copyright © 2015, Oracle and/or its affiliates. All rights reserved. | What’s new in MySQL 5.7 2525 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
- 26. Copyright © 2015, 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
- 27. Copyright © 2015, Oracle and/or its affiliates. All rights reserved. | Thank You
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