This document discusses using the MySQL Performance Schema to monitor and troubleshoot database performance issues. The Performance Schema collects instrumentation data without additional threads or memory beyond server startup. It contains tables to track statements, stages, waits, I/O and more. The document reviews Performance Schema options, tables and how to view summary statistics. Installing the SYS schema provides helpful views and stored procedures for exploring performance data in the Performance Schema.

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Troubleshooting with MySQL
Performance Schema
Ivan Ma
2015-01-10
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MySQL : Agenda
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Why and What – Performance Schema
Performance Schema Tables
Using MySQL Workbench
Try and See !
Questions
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Why Performance Schema?
System
Low throughput?
?
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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?

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What is Performance Schema
• The MySQL Performance Schema is a feature for monitoring MySQL Server
execution at a low level.
– to inspect internal execution of the server at runtime.
(Data Collection by Instrumentation at code level. No separate threads.)
– implemented using the PERFORMANCE_SCHEMA storage engine
– to monitor server events. An “event” is anything the server does that takes time and
has been instrumented so that timing information can be collected.
• Tables in the performance_schema database are views or temporary tables
that use no persistent on-disk storage.
• No memory allocation is done beyond that which occurs during server
startup
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The Journey : Then and now..
• MySQL 5.5
(1st Release P_S)
• Only waits events
– Mutex waits
– Conditions waits
– R/W locks waits
– File I/O waits
• Setup_(timers/consumers
/instruments) tables
• Few summary tables
• 17 Tables and 218
Instruments
• MySQL 5.6
• Statements and stages
• Table, Index and network
I/O. Table locks
• Host Cache
• User, account, host
• Setup_(actor/objects)
• Multiple summary tables
• Events’ hierarchy
• 52 Tables and 550
Instruments
• MySQL 5.7 (DMRs)
• Instrumentation:
– Transactions
– Metadata locks
– Prepared statements
– Stored programs
– Memory usage
• User variables
• Replication summary tables
• 76 Tables and 885
Instruments
• …
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MySQL performance_schema Database
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MySQL 5.6 Performance Schema Tables
• setup_% tables
• event_% tables
– Category
• stage
• statement
• wait
– Type
• current
• history
• Summary Tables
• Instances tables
• Connection tables
• Misc Tables
– host cache table
– performance timers
– threads
– users
– session*attrs
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Some notes with Using MySQL Workbench
• Default SQL Editor with
MySQL Workbench is
using ‘Safe update mode’
– Edit  Perference
• Why care –
– With Performance Schema,
No KEY
– Update setup_% tables may
not have ‘key’ on where
clause
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Performance Schema Options …(1)
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Performance Schema Options …(2)
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Performance Schema Options …(3)
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Default P_S setup_consumer
• Only a few instrumentation is ON
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setup_actor
• (HOST, USER, ROLE) default with (‘%’, ‘%’, ’%’)
• All foreground threads are monitored.
• Update to this table has no change to existing started threads.
• Demo
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Summary Tables
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Getting statements summary by account (e.g. ‘tpcc’)
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Why the SQL takes so long to run …
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At this moments
• We see
– How we can enable Performance Schema
– What to see (enable what you want to see to reduce the overhead)
• e.g. Only the session with the user login
– Statement taking too long to run
• What about “Wait Time”, “IO Time”, “Thread”, “Internal Stages”
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A Better way to look at this by using sys schema
• Using MySQL Workbench
– The first time clicking the Performance Schema Setup  Install SYS schema
• SYS Schema
– A set of VIEWs on the Performance Schema
– A set of SPs to make things easier
• to clean up performance schema tables
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Summary
• Using Performance Schema
– Data Collection
– As a tools
– Overhead! Enable what you want to see.
• Using SYS Schema
– Friendly VIEWs to explore performance data set
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