What type of storage engine a MySQL tables uses?


MySQL supports several storage engines such as InnoDB, MyISAM, BLACKHOLE, CSV. Depending on your use case, you might configure your MySQL table to use certain storage engine. To see the list of storage engines MySQL supports, simply run “SHOW ENGINES\G” under a mysql prompt.

To find out the particular storage engine used by a table, run the ‘show table status’ command for the named table as below. The first example is the mysql user table, which uses InnoDB –


mysql> use mysql;

mysql> show table status like 'user' \G
*************************** 1. row ***************************
Name: user
Engine: InnoDB
Version: 10
Row_format: Compact
Rows: 1
Avg_row_length: 16384
Data_length: 16384
Max_data_length: 0
Index_length: 49152
Data_free: 10485760
Auto_increment: 2
Create_time: 2013-08-26 22:52:09
Update_time: NULL
Check_time: NULL
Collation: binary
Checksum: NULL
Create_options:
Comment:
1 row in set (0.00 sec)

A sample table which uses MyISAM storage engine –


mysql> show table status like 'servers' \G
*************************** 1. row ***************************
Name: servers
Engine: MyISAM
Version: 10
Row_format: Fixed
Rows: 0
Avg_row_length: 0
Data_length: 0
Max_data_length: 433752939111120895
Index_length: 1024
Data_free: 0
Auto_increment: NULL
Create_time: 2013-08-24 01:42:15
Update_time: 2013-08-24 01:42:15
Check_time: NULL
Collation: utf8_general_ci
Checksum: NULL
Create_options:
Comment: MySQL Foreign Servers table
1 row in set (0.00 sec)

A table for logging slow queries is stored in a CSV storage engine –


mysql> show table status like 'slow_log' \G
*************************** 1. row ***************************
Name: slow_log
Engine: CSV
Version: 10
Row_format: Dynamic
Rows: 2
Avg_row_length: 0
Data_length: 0
Max_data_length: 0
Index_length: 0
Data_free: 0
Auto_increment: NULL
Create_time: NULL
Update_time: NULL
Check_time: NULL
Collation: utf8_general_ci
Checksum: NULL
Create_options:
Comment: Slow log
1 row in set (0.00 sec)

 

Features of some of the storage engines –

  • InnoDB: is a transaction-safe (ACID compliant) storage engine for MySQL that has commit, rollback, and crash-recovery capabilities to protect user data. 
  • MyISAM: These tables have a small footprint. Table-level locking limits the performance in read/write workloads, so it is often used in read-only or read-mostly workloads in Web and data warehousing configurations.
  • Memory: Stores all data in RAM, for fast access in environments that require quick lookups of non-critical data.
  • CSV: Its tables are really text files with comma-separated values. CSV tables let you import or dump data in CSV format, to exchange data with scripts and applications that read and write that same format.
  • Archive: These compact, unindexed tables are intended for storing and retrieving large amounts of seldom-referenced historical, archived, or security audit information.
  • Blackhole: The Blackhole storage engine accepts but does not store data, similar to the Unix /dev/null device. Queries always return an empty set.

 

References –

https://dev.mysql.com/doc/refman/8.0/en/storage-engines.html

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