MySQL double-write buffering principle and its optimization application in database development

MySQL double-write buffering principle and its optimized application in database development

With the rapid development of the Internet, the database, as an important part of the back-end system, carries a large number of data read and write operations. In order to improve the performance and stability of the database, MySQL introduced a double write buffer mechanism, which has become one of the important optimization methods in database development. This article will introduce the working principle of MySQL double-write buffering and give code examples to demonstrate its optimization application in database development.

1. The working principle of double-write buffering

MySQL's double-write buffering mechanism was introduced to solve the efficiency problem of writing dirty pages of memory pages back to disk. In the traditional database architecture, when dirty pages (that is, modified data in memory pages) need to be flushed back to disk, the dirty pages need to be written to the redo log of the disk first, and then written to the data file of the disk. . Such write operations will cause multiple disk IOs and affect the performance of the database.

The introduction of the double-write buffering mechanism writes the dirty pages to the double-write buffer of the memory first, instead of writing them directly to the redo log. During the process of writing the redo log, the dirty pages are also processed. The checkpoint flush operation writes dirty pages to the data file on the disk at once. This reduces disk IO operations and improves database write performance.

2. Optimized application of double-write buffer

1. Configuring double-write buffer

In the MySQL configuration file my.cnf, we can pass parameters innodb_doublewrite to configure the opening and closing of double write buffering. By default, double-write buffering is enabled, which is also the officially recommended configuration. We can turn off the double write buffer by adding the following configuration to my.cnf:

innodb_doublewrite = 0

2. Monitor the usage of the double write buffer

MySQL's performance monitoring tool Performance Schema provides some related tables and views. We can use these tools to monitor the usage of double-write buffers and discover and solve potential problems in a timely manner.

The following is a sample code for querying double-write buffer related tables in Performance Schema:

SELECT
    variable_name,
    variable_value
FROM
    performance_schema.variables_info
WHERE
    variable_name = 'innodb_doublewrite'
OR variable_name = 'innodb_doublewrite_io_threads'
OR variable_name = 'innodb_doublewrite_pages'
;

3. Optimize physical database design

Through a reasonable physical database Designed to further optimize the performance of double write buffering. For example, you can separate frequently written tables from infrequently written tables and place them in different data files. This can reduce the burden of double-write buffering and improve database performance.

The following is a physical database design sample code:

CREATE TABLE frequent_table(
    ...
)
ENGINE = InnoDB
PARTITION BY KEY(id)
PARTITIONS 8
;

CREATE TABLE infrequent_table(
    ...
)
ENGINE = InnoDB
PARTITION BY KEY(id)
PARTITIONS 4
;

Through reasonable partition design, frequently written tables and infrequently written tables are divided into different data files. , reducing the write pressure of the double write buffer.

Summary:

MySQL double-write buffering mechanism is an important optimization method introduced to improve the writing performance of the database. By writing dirty pages into the memory buffer and flushing checkpoints while writing the redo log, disk IO is reduced and database performance is improved. In database development, the performance and stability of the database can be further improved by properly configuring and monitoring the usage of double-write buffers, and optimizing the physical database design.

(The above content is for reference only, the specific optimization application needs to be adjusted and optimized according to the actual situation.)

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