Storage engine analysis

Storage engine

MySQL Architecture ：

The storage engine is to store data 、 Index 、 to update / Implementation of query data and other technologies . The storage engine is based on tables rather than libraries , So the storage engine can also be called the table engine . The default storage engine is InnoDB.

The relevant operation ：

--  Query table creation statement show create table account;--  Specify the storage engine when creating the table CREATE TABLE  Table name (  ...) ENGINE=INNODB;--  View the storage engines supported by the current database show engines;

InnoDB

InnoDB It is a general storage engine with high reliability and high performance , stay MySQL 5.5 after ,InnoDB By default MySQL engine .

characteristic ：

• DML Operation follows ACID Model , Support Business
• Row-level locks , Improve concurrent access performance
• Support Foreign keys constraint , Ensure the integrity and correctness of data

file ：

• xxx.ibd: xxx Representative table name ,InnoDB Each table of the engine will correspond to such a tablespace file , The table structure that stores the table （frm、sdi）、 Data and index .

Parameters ：innodb_file_per_table, Decide whether multiple tables share a tablespace or each table corresponds to a tablespace

Knowledge point ：

see Mysql Variable ：show variables like 'innodb_file_per_table';

from idb File extraction table structure data ：（ stay cmd function ）ibd2sdi xxx.ibd

InnoDB Logical storage structure ：

MyISAM

MyISAM yes MySQL Early default storage engine .

characteristic ：

• Unsupported transaction , Foreign key not supported
• Support table lock , Row locks are not supported
• Fast access

file ：

• xxx.sdi: Store table structure information
• xxx.MYD: Store the data
• xxx.MYI: Storage index

Memory

Memory The table data of the engine is stored in memory , Affected by hardware problems 、 The impact of power failure , These tables can only be used as temporary tables or caches .

characteristic ：

• Store in memory , Fast
• hash Indexes （ Default ）

file ：

• xxx.sdi: Store table structure information

Storage engine features

Choice of storage engine

When choosing a storage engine , The appropriate storage engine should be selected according to the characteristics of the application system . For complex applications , You can also select a variety of storage engines to combine according to the actual situation .

• InnoDB: If the application has higher requirements for the integrity of things , Data consistency is required under concurrent conditions , Data operations in addition to inserts and queries , It also contains a lot of updates 、 Delete operation , be InnoDB It 's a better choice
• MyISAM: If the application is based on read operation and insert operation , There are very few update and delete operations , And the integrity of the transaction 、 The requirement of concurrency is not high , Then this storage engine is very suitable .
• Memory: Keep all data in memory , Fast access , Usually used for temporary tables and caches .Memory The limitation of table size is the limitation of table size , Too large tables cannot be cached in memory , And can't guarantee the security of data

Footprints and comments in e-commerce are suitable for MyISAM engine , Cache is suitable for Memory engine .