Database composition storage engine

3.2　MySQL Storage engine

Storage engine in MySQL The bottom layer is provided in the form of components , Storage mechanisms provided by different storage engines 、 The storage mode of the index is different from the lock granularity . This section is right MySQL A brief introduction to the commonly used storage engines in .

3.2.1　 see MySQL Storage engine in

Can be in MySQL Enter the following command on the command line , View the current MySQL Supported storage engines .

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mysql> SHOW ENGINES \G*************************** 1. row ***************************      Engine: ARCHIVE     Support: YES     Comment: Archive storage engineTransactions: NO          XA: NO  Savepoints: NO*************************** 2. row ***************************      Engine: BLACKHOLE     Support: YES     Comment: /dev/null storage engine (anything you write to it disappears)Transactions: NO          XA: NO  Savepoints: NO*************************** 3. row ***************************      Engine: MRG_MYISAM     Support: YES     Comment: Collection of identical MyISAM tablesTransactions: NO          XA: NO  Savepoints: NO*************************** 4. row ***************************      Engine: FEDERATED     Support: NO     Comment: Federated MySQL storage engineTransactions: NULL          XA: NULL  Savepoints: NULL*************************** 5. row ***************************      Engine: MyISAM     Support: YES     Comment: MyISAM storage engineTransactions: NO          XA: NO  Savepoints: NO*************************** 6. row ***************************      Engine: PERFORMANCE_SCHEMA     Support: YES     Comment: Performance SchemaTransactions: NO          XA: NO  Savepoints: NO*************************** 7. row ***************************      Engine: InnoDB     Support: DEFAULT     Comment: Supports transactions, row-level locking, and foreign keysTransactions: YES          XA: YES  Savepoints: YES*************************** 8. row ***************************      Engine: MEMORY     Support: YES     Comment: Hash based, stored in memory, useful for temporary tablesTransactions: NO          XA: NO  Savepoints: NO*************************** 9. row ***************************      Engine: CSV     Support: YES     Comment: CSV storage engineTransactions: NO          XA: NO  Savepoints: NO9 rows in set (0.00 sec)

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Results show , At present MySQL In all 9 Storage engine , except FEDERATED Outside the storage engine , And support 8 Storage engine .

Be careful ： The author's MySQL Version is 8.0.18.

3.2.2　 Common storage engine introduction

MySQL The storage engines commonly used in are InnoDB、MyISAM、MEMORY、ARCHIVE and CSV, This section gives a brief introduction to these storage engines .

1．InnoDB Storage engine

InnoDB The characteristics of the storage engine are as follows ：

· Support transactions .

· The lock level is row lock , Than MyISAM The storage engine supports higher concurrency .

· Able to recover data through binary logs .

· Support foreign key operation .

· On index storage , The index and data are stored in the same file , The default in accordance with the B+Tree Organize the structure of the index . meanwhile , The leaf node of the primary key index stores complete data records , The leaf node of the non primary key index stores the value of the primary key .

· stay MySQL 5.6 After the version , By default InnoDB Storage engine .

· stay MySQL 5.6 After the version ,InnoDB The storage engine supports full-text indexing .

2．MyISAM Storage engine

MyISAM The characteristics of the storage engine are as follows ：

· Unsupported transaction .

· The lock level is table lock , It is not applicable in scenarios requiring high concurrency .

· If the data file is damaged , Difficult to recover data .

· Foreign key not supported .

· On index storage , The index file is separated from the data file .

· Full text index support .

3．MEMORY Storage engine

MEMORY The characteristics of the storage engine are as follows ：

· I won't support it TEXT and BLOB data type , Only fixed length string types are supported . for example , stay MEMORY In the storage engine , Will VARCHAR The type is automatically converted to CHAR type .

· The lock level is table lock , In high concurrency scenarios, it will become a bottleneck .

· It is usually used as a temporary table , Intermediate results are generated when storing query data .

· Data stored in memory , Data will be lost after restarting the server . If it is data that needs persistence , Not suitable for storage in MEMORY In the data table of the storage engine .

4．ARCHIVE Storage engine

ARCHIVE The characteristics of the storage engine are as follows ：

· Support data compression , Before storing data, the data will be compressed , Suitable for storing archived data .

· Only data insertion and query are supported , After inserting data , Data cannot be changed or deleted , Only query .

· It only supports adding indexes to fields of integer auto increment type .

5．CSV Storage engine

CSV The characteristics of the storage engine are as follows ：

· The main storage is .csv Formatted text data , You can directly open the stored file for editing .

· Can be MySQL The data in a data table in is directly exported as .csv file , Can also be .csv Import the file into the data table .

Be careful ： The author just listed MySQL Some storage engines commonly used in , Knowledge of other storage engines , Readers can refer to MySQL Official documents for understanding and learning , Address the following ：

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

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