What are the techniques for learning MySQL query caching and performance optimization?

What are the query caching and performance optimization techniques for learning MySQL?

In MySQL, query caching and performance optimization are very important aspects. They can significantly improve the query efficiency and performance of the database. This article will introduce the query caching mechanism in MySQL and some common performance optimization techniques, with code examples.

1. Query cache

Query cache is an important feature in MySQL. It can cache query results and avoid repeated queries to the database. After a query statement is executed, MySQL will store the query results in the query cache in memory. If the same query statement is executed next time, MySQL will directly return the results from the query cache without querying the database again. This can Greatly improve query efficiency.

However, query caching is not suitable for all scenarios, and in some cases it will reduce performance. The following are some precautions and optimization tips for using query cache:

1. Opening and closing query cache

In the MySQL configuration file, turn it on by setting the query_cache_type parameter Or turn off query caching. You can view the status and settings of the query cache through the following code example:

SHOW VARIABLES LIKE 'query_cache_type';
SET GLOBAL query_cache_type = 0;

Among them, the query_cache_type parameter value is 0 to turn off the query cache, and 1 to turn on the query cache.

2. The hit rate of the query cache

The effect of the query cache mainly depends on the hit rate of the query cache. When the query statement finds the corresponding result in the cache, the hit rate increases. You can view the hit rate of the query cache through the following code example:

SHOW STATUS LIKE 'Qcache_hits';
SHOW STATUS LIKE 'Qcache_inserts';
SHOW STATUS LIKE 'Com_select';

Among them, Qcache_hits represents the number of query cache hits, Qcache_inserts represents the number of query cache insertions, and Com_select represents the number of query statements executed.

3. Invalidation of query cache

When the table in the database is modified (including insert, update, and delete operations), the related query cache will become invalid. You can view the number of query cache invalidations through the following code example:

SHOW STATUS LIKE 'Qcache_not_cached';

Among them, Qcache_not_cached indicates the number of times the query does not use the cache.

2. Performance optimization techniques

In addition to query caching, there are some other performance optimization techniques that can improve MySQL query efficiency. The following are some commonly used performance optimization tips:

1. Using indexes

Indexes are one of the important means to speed up queries. By creating indexes on table columns, you can quickly locate qualified data rows and avoid full table scans. You can create an index through the following code example:

CREATE INDEX index_name ON table_name (column_name);

where index_name is the name of the index, table_name is the name of the table, and column_name is the name of the column.

2. Optimizing query statements

Optimizing query statements is the key to improving query efficiency. Query statements can be optimized in the following ways:

• Reduce the number of results returned by the query statement and only return the required data columns;
• Try to use primary key or unique index conditions and avoid using all Table scan;
• Use appropriate relational operators, such as equal to, greater than, less than, etc.;
• Avoid using subqueries or nested queries, and try to use join queries.

3. Set the appropriate buffer size

There are multiple buffers in MySQL that can be used to optimize query performance, such as query cache, connection buffer, and sorting Buffer etc. Query efficiency can be improved by sizing these buffers appropriately. The following are some commonly used buffer parameters and code examples:

• Query cache size: query_cache_size, the default is 0;
• Connection buffer size: join_buffer_size, the default is 256KB;
• Sort buffer size: sort_buffer_size, the default is 2MB.

Set the buffer size through the following code example:

SET GLOBAL query_cache_size = 1024 * 1024 * 100; -- 设置查询缓存大小为100MB
SET GLOBAL join_buffer_size = 1024 * 256; -- 设置连接缓冲区大小为256KB
SET GLOBAL sort_buffer_size = 1024 * 1024 * 2; -- 设置排序缓冲区大小为2MB

Summary:

Learning MySQL query caching and performance optimization techniques is to improve database query efficiency and performance important step. By rationally using the query cache, optimizing query statements, and setting appropriate buffer sizes, MySQL query efficiency can be effectively improved.

The above are some introductions and code examples about learning MySQL query caching and performance optimization techniques. Hope this helps!

The above is the detailed content of What are the techniques for learning MySQL query caching and performance optimization?. For more information, please follow other related articles on the PHP Chinese website!