MyBatis Caching Explained: First & Second Level

The caching mechanism of MyBatis is an object-based caching mechanism that can effectively improve query performance. There are three main types of caching mechanisms in MyBatis.

1. First-level cache: The first-level cache is at the SqlSession level. When a query is executed in a SqlSession, the results are stored in the memory of that SqlSession. If the same query is executed again, MyBatis will directly get the results from the cache, avoiding repeated database queries.
2. Level 2 cache: The level 2 cache is at the Mapper level, where multiple SqlSessions can share the same Mapper’s level 2 cache. When a SqlSession executes a query, the results will be cached in the Mapper’s level 2 cache, allowing other SqlSessions to retrieve the results from it.
3. Cache invalidation: performing operations such as insert, update, delete, etc. will cause the cache to become invalid. MyBatis will clear the relevant cache data to ensure consistency between cache data and database data.

By properly configuring and utilizing caching mechanisms, it is possible to effectively enhance query performance, reduce the frequency of database accesses, and improve the overall performance and stability of the system.