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 .