4. Storage Engine: MyISAM
Table lock
No automated data recovery
No transactions
Only indexes are cached in memory
Compact storage
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5. Storage Engine: InnoDB
Transactional
Foreign keys
Multiversioning
Clustered by primary key
No cached count(*)
Blocking AUTO_INCREMENT
Optimized cache
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6. InnoDB Storage Architecture
Tablespaces Segment
leaf node segment
extent extent
non-leaf node segment
extent extent
rollback node segment
...
Extent
Row
Page
trx id
row row
row id
row row
roll pointer
...
col 1 ... col n 64 pages
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7. InnoDB and File system
File
system
-‐>
InnoDB
-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐-‐
disk
partition
-‐>
tablespace
file
-‐>
segment
inode
-‐>
fsp0fsp.c
'inode'
fs
space
allocation
unit
-‐>
extent
disk
block
-‐>
page
(16
kB)
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15. B+tree indexes: Demo
CREATE TABLE People (
last_name varchar(50) not null,
first_name varchar(50) not null,
dob date not null,
gender enum('m', 'f') not null,
key(last_name, first_name, dob)
);
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17. B+Tree: Types of queries
Match the full value
where last_name=? and first_name=? and bod=?
Match a leftmost prefix
where last_name=?
where last_name=?
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18. B+Tree: Types of queries
Match a column prefix
where last_name like ”Liang%”
Match a range of values
where last_name > ?
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19. B+Tree: Types of queries
Match one part exactly and match a range
on another
where last_name=? and first_name>?
Index only queries
select first_name where last_name=?
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20. B+Tree: Limitations
Doesn’t start from leftmost
where first_name=?
Skip columns in the index
where last_name=? and bod=?
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21. B+Tree: Limitations
More than one range conditions
where last_name>? and first_name>?
Can’t optimize to the right of the first range
conditon
where last_name>? and first_name=?
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26. Useful commands
show index from TABLE;
explain [extended] SELECT * FROM TABLE;
UPDATE, DELETE convert to SELECT
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27. Explain
select_tpe
simple, primary, subquery, derived, union
type
all < index < range < ref < eq_ref < const,
system < null
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28. Explain
Extra
using where
using index
using filesort
using temporary
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