How to use caching technology in MySQL to increase read speed?

How to use caching technology in MySQL to improve reading speed?

With the continuous increase in the amount of data and the increase in system access frequency, the execution efficiency of database query statements has become one of the key factors affecting system performance. As a commonly used relational database management system, MySQL provides a variety of caching technologies to optimize query performance, including query caching.

Query caching is one of the simplest and most basic caching technologies in MySQL. It improves performance by storing the results of queries in memory so that when the same query is repeatedly executed, the results in the cache can be returned directly. Reading speed. The following will introduce in detail how to use query cache in MySQL to optimize query performance.

First, you need to ensure that the query cache is turned on. In the MySQL configuration file (usually my.cnf), find and modify the following configuration items:

query_cache_type = 1
query_cache_size = 64M

Among them, query_cache_type=1 means enabling query Cache, query_cache_size specifies the size of the query cache, here it is set to 64MB. After completing the modification, restart the MySQL service to make the configuration take effect.

Next, you need to add a cache command before the query statement that needs to use the query cache.

For example, to query the record with ID 1 in the table named "users", you can use the following statement:

SELECT * FROM users WHERE id = 1;

In order to enable query caching, you can add the "SQL_CACHE" keyword before the query statement, as follows:

SELECT SQL_CACHE * FROM users WHERE id = 1;

In this way, MySQL will query The results are cached in memory.

In addition, you can also control the cache validity period by setting the cache expiration time. In MySQL, the default cache expiration time is one hour, which can be modified through the following configuration items:

query_cache_limit = 1M
query_cache_min_res_unit = 512

Among them, query_cache_limit specifies the cache result Size limit, here set to 1MB, query_cache_min_res_unit represents the minimum unit of cached results, here set to 512 bytes. Set the values ​​of these two parameters according to actual needs.

In addition, you can also control whether to use the query cache by using the cache flag. In MySQL, you can use SQL_NO_CACHE to disable the query cache, as follows:

SELECT SQL_NO_CACHE * FROM users WHERE id = 1;

In this way, MySQL will query the results directly from the database, and The query cache will not be used.

It should be noted that the query cache is only useful for queries that are frequently queried and whose results do not change frequently. If the queried data is frequently modified, the query cache will cause a large number of cache invalidations and update operations, which will in turn reduce query performance.

To sum up, using query cache can significantly improve the reading speed of MySQL and reduce the access pressure on the database. However, when configuring and using it, you need to carefully consider the frequency of queries and the variability of data to avoid unnecessary cache invalidation and maintenance operations. In actual applications, relevant tuning can be performed based on specific business requirements and system performance.

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