Cache
Mybatis level cache is a scope with SqlSession , in the same sqlSession executed twice in the same sql statement data for the first time will be finished in a database query written to the cache (memory), the second will get from the cache data will no longer be from the database query to improve query efficiency. When a sqlSession after the end of the sqlSession in the cache would not exist. Mybatis enabled by default cache.
simply say
session level cache
When a user on the same session when multiple queries, only one database query
The query returns directly behind cached data
When submitting a transaction ends session data in the cache will clear
Secondary cache
Mybatis secondary cache is a plurality SqlSession shared, which scope is mapper same one namespace , different sqlSession performed twice same namespace in the sql statement and to sql passing the same parameters i.e., perform the same final sql statement of once finished will be a database query data is written to the cache (memory), the second gets the data from the cache will not be from a database query to improve query efficiency. Mybatis not enabled by default in the secondary cache requires setting configuration parameters enable a second global cache.
The working principle is that when opened the second-level cache , the mybatis will cache data is serialized to disk
When starting a new session when the query again tries to query from a second-level cache whether there is data,
There are direct return data in the cache.
Open second-level cache
Increased need to open the secondary cache table mapping file cache tag
