What is the purpose of mybatis cache?

The purpose of MyBatis cache is to improve query performance and reduce the number of database accesses. It stores query results in memory, so when the same query is executed again, it can directly retrieve the results from the cache without needing to access the database again. This significantly reduces the number of database accesses and improves system response time.

MyBatis cache is divided into two levels: first-level cache and second-level cache.

1. First-level cache: by default, it is enabled and is at the SqlSession level, meaning it is only valid within the same SqlSession. When executing the same query, MyBatis will first search for the result in the first-level cache. If found, it will be returned directly. If not found, the query will be executed and the result will be stored in the cache. The first-level cache is enabled by default and cannot be disabled.
2. Second-level cache: It is a cache at the Mapper level that can share cached results across SqlSessions. When executing a query, MyBatis will first look for the result in the second-level cache. If found, it will return it directly. If not found, it will execute the query and store the result in the cache. Second-level cache needs to be manually configured and attention should be paid to data consistency in the cache.

In general, MyBatis caching can significantly improve system performance, reduce database access pressure, but also pay attention to the consistency issue of cached data.