Sharing of data caching technology in MySQL

MySQL is one of the most widely used relational databases at present. It has the advantages of high efficiency, stability, strong scalability, and support for multiple development languages. In MySQL, data caching technology is one of the important means to improve performance. This article will share with readers the data caching technology in MySQL.

1. The importance of caching

First of all, we need to understand the importance of caching. In MySQL, caching can shorten the time of data query and improve response speed and efficiency. MySQL uses caching technology to greatly reduce database I/O operations, thereby improving the performance of the entire application.

In MySQL, the caching mechanism is divided into query cache and InnoDB Buffer Pool. Query cache refers to MySQL's own caching mechanism, which can save query results in memory to speed up the return of the same query results next time, thereby saving disk I/O time. The InnoDB Buffer Pool is a memory pool used to store table data and indexes. The application's data access to the InnoDB storage engine can be obtained from the Buffer pool, or the modified data can be postponed to later operations.

2. Query cache

MySQL's query cache will first check whether the request hits the cache. If it hits, the query result will be returned directly from the cache; if it does not hit the cache, you need Execute the query and store the query results in the cache for the next query.

However, query caching also has flaws. When a database table is updated, all query caches corresponding to the table will be cleared, so the default setting of the query cache is disabled. If the update frequency of the table is relatively high, the query cache will actually reduce the query speed.

3. InnoDB Buffer Pool

InnoDB Buffer Pool is a memory cache area used to cache table data and indexes in the InnoDB storage engine. In the InnoDB storage engine, all data is stored on disk and is stored in the form of pages. Normally, the data contained in cache pages in memory is read from disk.

When the application needs to query data, InnoDB will first query whether the data to be queried exists in the Buffer Pool. If it exists, it will be obtained directly from the memory. Otherwise, the data will be read from the disk to the Buffer Pool. The data is then returned to the application.

The size of the InnoDB Buffer Pool can be adjusted through the parameter innodb_buffer_pool_size. Generally speaking, setting it to 70% - 80% of the physical memory is a more appropriate choice. In addition, we can also use the show engine innodb status command to check the usage of the Buffer Pool to determine whether adjustments need to be made.

4. Optimizing cache performance

When using caching technology in MySQL, we need to pay attention to the following aspects to optimize cache performance.

(1) Reasonably set cache capacity and cache elimination strategy. Properly setting the cache size and cache elimination strategy can reduce memory usage and improve MySQL query performance.

(2) Avoid cache penetration. Cache penetration is when a large amount of data is queried for data that does not exist in the cache, which causes the query to keep making requests to disk. An effective way is to use Bloom filters to filter data and reduce invalid queries.

(3) Avoid cache avalanche. Cache avalanche means that within a certain period of time, a large amount of cached data fails at the same time, causing a large number of requests to fall directly on the database, causing a sudden increase in database pressure and causing server downtime. The solution is generally to use a multi-level caching mechanism to layer the cache, thereby reducing the risk of cache avalanche.

(4) Use non-blocking cache operations. In high concurrency situations, using blocking cache operations can impact overall application performance. Therefore, it is recommended to use non-blocking cache operations to improve concurrency performance.

5. Summary

The data caching technology in MySQL is one of the important means to improve performance. This article mainly introduces the query cache and InnoDB Buffer Pool in MySQL, as well as related techniques for optimizing cache performance. In actual applications, it is necessary to reasonably set the cache size and cache elimination strategy based on specific business scenarios and hardware environments to improve system performance.

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