MySQL Indexing

1. MySQL Indexing
Dinh Hoang Long

2. About me
DINH HOANG LONG
Group Leader, Bridge Software Engineer
Interested in: PHP, Python, MySQL, Docker, Agile
You can find me at: @dinhhoanglong91

3. INDEXING OVERVIEW
B-tree, InnoDB, MyISAM
1

4. B-tree
10 11 120 1 14 15 16 18 197 853
2 4 6
13 17
9

5. B-tree
Time complexity
Algorithm Average Worst case
Search O(log n) O(n)
Insert O(log n) O(n)
Delete O(log n) O(n)

6. B-tree in MySQL
High Performance MySQL

7. MyISAM vs InnoDB
MyISAM
◦ Store rows on disk in the order which they were inserted
◦ Rows are fixed-size
◦ Find row by seeking the required number of bytes
from the beginning
Row number col1(PK) col2
0 99 8
1 12 56
2 3000 62

8. MyISAM vs InnoDB
MyISAM Primary Key Layout
High Performance MySQL

9. MyISAM vs InnoDB
MyISAM Secondary Key Layout
High Performance MySQL

10. There is no structural difference
between primary key and other index
A primary key is simple a unique, nonnullable index
named PRIMARY
MyISAM

11. MyISAM vs InnoDB
InnoDB - Clustered Index
◦ Rows are stored in the index’s leaf pages
◦ “Clustered”: Rows with adjacent key values are stored close to
each other

12. MyISAM vs InnoDB
Clustered Index Data Layout
High Performance MySQL

13. MyISAM vs InnoDB
InnoDB secondary index data layout
High Performance MySQL

14. Secondary indexes access require
two index lookups instead of one
You can have only one clustered index per table, because
you can’t store the row in two places at once
InnoDB

15. Single & Multiple columns Indexing2

16. Single column indexing
SELECT * FROM users WHERE id = 1;
SELECT * FROM users WHERE id + 1 = 2;

17. Hash index strategy for large column
INSERT INTO users(email, email_crc32, name)
VALUES('long@gmail.com', CRC32('long@gmail.com'), 'Long');

18. Hash index strategy for large column
INSERT INTO users(email, email_crc32, name)
VALUES('long@gmail.com', CRC32('long@gmail.com'), 'Long');
SELECT * FROM users
WHERE email_crc32 = CRC32('long@gmail.com')
AND EMAIL = 'long@gmail.com';

19. Multiple columns indexing
High Performance MySQL

20. Match a leftmost prefix
Match one part exactly and match a
range on another part
InnoDB

21. Multiple columns indexing
Index Condition Pushdown (ICP)

22. Searching index tree instead of
Full table scan
ICP

23. EXPLAIN to understand your query3

24. Thank you for watching!
ANY QUESTIONS?

25. References
◦ High Performance MySQL, 3rd Edition
◦ MySQL Indexing
https://viblo.asia/dinhhoanglong91/posts/PDOkqWxAGjx
◦ Sử dụng EXPLAIN để tối ưu câu lệnh MySQL
https://viblo.asia/dinhhoanglong91/posts/BYjv44gmvxpV
◦ MySQL Index Condition Pushdown
https://viblo.asia/dinhhoanglong91/posts/ZjlealAZGqJ