This presentation speaks about the ways to optimize queries and the best practices

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2. MySQL Query Optimization
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MySQL Introduction
Storage Engines
InnoDB
Optimization Types
Query Optimization
Explain Plan
Indexing
Rewriting Queries
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3. MySQL Introduction
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Open Source
RDBMS
Released in 1995
Founded by Monty
Current Version 5.5
Most Widely Used DB
Forks - Percona, MariaDB , Drizzle
Facebook, Twitter , Wikipedia, Walmart, ebay.
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4. Storage Engines
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Prominent Feature of MySQL
Depends on Needs
MyISAM and INNODB
MyISAM – Non Transactional
Innodb - Transactional
Others – Memory, CSV, Merge , NDB Cluster
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5. InnoDB
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Founded in 1995 by Innobase.
Transactional Support
Row level locking
Foreign Key support
Clustered Index
Current Version 1.1
Forks – XtraDB , Falcon , MariaDB , TokuDB
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6. InnoDB
Primary Key
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Clustered index needs a Primary Key.
If not InnoDB creates a hidden Primary key.
Column must be small .
It is better to have auto-increment columns.
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7. Optimization Types
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Hardware & OS Optimization
Query Optimization
Server Optimization
Application Optimization
Network Optimization
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8. Query Optimization
Need For Query Optimization.
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Performance drops as data grows.
Hardware Optimization 5X Performance.
Query Optimization 10X to 100 X .
Reduces load on servers.
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9. Query Optimization
Techniques To Optimize Queries ?
• Indexing .
• Rewriting Queries.
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10. Example
CREATE TABLE `EVENT_TRAIL_NEW` (
`ID` bigint(20) NOT NULL AUTO_INCREMENT,
`SOURCE_SYSTEM_ID` bigint(20) NOT NULL,
`TARGET_SYSTEM_ID` bigint(20) NOT NULL,
`EVENT_SITUATION_CATALOG_ID` bigint(20) NOT NULL,
`PREVIOUS_EVENT_ID` bigint(20) DEFAULT NULL,
`secure_token` varchar(100) DEFAULT NULL,
`event_timestamp` datetime DEFAULT NULL,
`current_state` varchar(25) NOT NULL,
`event_correlation_id` bigint(20) DEFAULT NULL,
PRIMARY KEY (`ID`)
) ENGINE=InnoDB AUTO_INCREMENT=8561335 DEFAULT CHARSET=ucs2
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11. Explain Plan
• An inbuilt tool to see query performance.
• Shows estimated query performance.
• Works only for select queries.
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12. Explain Plan
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Complex Query Example.
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13. Indexing
• Index (Key) are used to find rows quickly.
• Powerful way to tune queries.
• Increases the performance of select, update and
delete queries.
• Reduces disk IO .
• Optimal index requires query rewrite 
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14. Indexing
Myths of Index :
• Increases the database size.
• Indexing will decrease the insert query
performance.
• One index per table query.
• Poor performance with wild card characters.(%,$).
• Make index length small ( 767 bytes InnoDB).
• Do not work on full table scans.
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15. Indexing
Types of Index :
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Primary
Unique
Secondary index.
Full Text Index ( MyISAM )
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16. Indexing
B – Tree:
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Balanced Tree (not Binary Tree).
Used in all databases.
All the secondary indexes.
Suitable for most needs.
Re-indexing is not required.
Used when queries scans less than 30% of available
data approximately
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17. Indexing
B- Tree Works On:
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Full value.
Range values.
Perfix values. Ex) Mysql% , M%.
Use of functions on indexed columns disables it
usage in most cases.
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18. Indexing
Example :
Table
: EVENT_TRAIL_NEW
Column
: event_timestamp
Min value
: 2011-07-20 12:30:40
Max Value
: 2012-11-27 23:00:00
Index name : idx_event_timestamp
Count of rows : 8560301
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19. Indexing
Example (Range Values )
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20. Indexing
Example ( Function )
Without date()
With date()
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21. Indexing
Example (prefix usage).
• Table
: EVENT_TRAIL_NEW
• Column
: current_state
• Index name : idx_current_state
• Count of rows : 8560301
Unique Values
• COMPLETE
• EMITTED
• EXCEPTION
• RE_EMITTED
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22. Indexing
Example ( Prefix Usage )
Search by Prefix :
Search by Suffix :
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23. Indexing
Example (One index per table query )
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Table
: EVENT_TRAIL_NEW
Column
: TARGET_SYSTEM_ID
Index name : idx_TARGET_SYSTEM_ID
Count of rows : 8560301
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24. Rewriting Queries
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Make Use Of Index .
Poorly Written .
Fetching Too Many Rows.
Fetching Unwanted Column.
Improperly Arranged.
Sort on Primary Key.
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25. Rewriting Queries
• In Query Optimization
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26. Rewriting Queries
• In Query Optimization ( Use Joins)
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27. Rewriting Queries
• Removing Functions.
Date() is removed on Right side.
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28. THANKS …
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