How to clear mysql cache

How to clear the cache in MySQL requires specific code examples

Cache is one of the important performance optimization technologies in the MySQL database. MySQL uses cache to store frequently queried data and query results to improve the reading speed of the database. However, in some cases, query results may be inaccurate or outdated due to the presence of cache. To solve this problem, we can manually clear the MySQL cache.

MySQL's cache is generally divided into two types: query cache and InnoDB cache. Here's how to clear these two caches.

1. Query cache

Query cache is one of MySQL's built-in caching mechanisms, which caches the results of queries. Turning on query caching can improve the reading speed of the database, but if the data changes frequently, the cached data may be inaccurate.

To clear the query cache, we can use the RESET QUERY CACHE command.

RESET QUERY CACHE;

This command will immediately clear all data in the query cache and start caching query results again.

2. InnoDB Cache

The InnoDB cache is the cache used in MySQL to store tables and indexes. It improves the read performance of the database by using memory. However, unlike the query cache, the InnoDB cache cannot be cleared directly. However, we can achieve the effect of clearing the cache by modifying the parameters of InnoDB.

First, we need to restart the MySQL service, and then configure the InnoDB-related parameters in the my.cnf configuration file.

# 重启MySQL服务
sudo service mysql restart

Open the my.cnf file, find the [mysqld] configuration section, and then add the following lines of code to it:

# 清除InnoDB缓存
innodb_buffer_pool_size=0
innodb_flush_method=O_DIRECT
innodb_flush_log_at_trx_commit=2

Among them, innodb_buffer_pool_sizeIndicates the size of the InnoDB cache. Setting it to 0 means clearing the cache.

Save and close the my.cnf file, and then restart the MySQL service.

sudo service mysql restart

Through the above operations, we can clear the InnoDB cache.

It should be noted that after clearing the cache, MySQL performance may decrease because the database needs to reload data into the cache. Therefore, we need to weigh the pros and cons of clearing the cache and decide whether to perform the clearing operation based on the specific circumstances.

Summary:

MySQL's cache is one of the keys to improving database performance, but in some cases, you may need to manually clear the cache. For query cache, you can use the RESET QUERY CACHE command to clear the cache. For InnoDB cache, you can clear the cache by modifying relevant parameters. After clearing the cache, you need to pay attention to the decrease in database performance and weigh whether to perform the clearing operation based on the specific situation.

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