MySQL storage engine

Concept

Database storage engine is the bottom software organization of database , Database management system （DBMS） Create with data engine 、 Inquire about 、 Update and delete data .

• Different storage engines provide different storage mechanisms 、 Indexing techniques 、 Lock level and other functions . Now many different database management systems support many different data engines .MySQL The core is the storage engine
• Users can choose different storage engines for data tables according to different needs
• have access to SHOW ENGINES command , You can see MySQL All execution engines of , We can see that the default execution engine is innoDB Support transactions , Row level locking and foreign keys .

classification

• CSV: Logically, it is the storage engine of comma pink data . Special offer to create one for each data table in the database subdirectory .csv file . This is a normal text file , Each data line takes up one text line .CSV The storage engine does not support indexes .
• BlackHole： Black hole engine , Any data written will disappear , Generally used to record binlog Do replication relay
• ERFORMANCE_SCHEMA Storage engine ： The engine is mainly used for mobile database server performance parameters .
• Mrg_Myisam Merge Storage engine ： It's a group. Mylsam The combination of , in other words , He will be Myisam Multiple table aggregation engines , But he has no internal data , The real data is still Myisam In the engine's table , But you can query directly 、 Delete, update, etc .

function	MyISAM	MEMORY	InnoDB
Storage limits	256TB	RAM	64TB
Support transactions	No	No	Yes
Full text index support	Yes	No	No
Support B Tree index	Yes	Yes	Yes
Support hash index	No	Yes	No
Support cluster indexing	No	No	Yes
Support data indexing	No	Yes	Yes
Support data compression	Yes	No	No
Space support rate	low	N/A	high
Support foreign keys	No	No	Yes

operation

Query the storage engine supported by the current database

Method ：

SHOW ENGINES;

View the current default storage engine .

Method ：

SHOW VARIABLES LIKE '%storage_engine%';

See what engine a table uses （ In the real results, the parameters engine The latter indicates the current storage engine ）

Method ：

SHOW CREATE TABLE table_name;

Specify the storage engine when creating a new table

Method ：

CREATE TABLE(...) ENGINE = MYISAM;

Modify database engine

Method ：

ALTER TABLE table_name ENGINE = MYISAM;
ALTER TABLE table_name ENGINE = InnoDB;

modify MySQL Default storage engine

1. close MySQL service
2. find MySQL In the service installation directory my.ini file
3. find default-storage-engine=INNODB Change to target engine
4. start-up MySQL service