Matters needing attention:
1. The modification of user permissions by the administrator will not affect existing links
2. Disconnect long links periodically to prevent excessive storage space
In version 5.7 and above, manually execute mysql-reset-connection to re-initialize linked resources every time a large or complex operation is performed. This process does not require reconnection and permission verification
2, query cache: key-value form, key is the statement, value is the result,
Disadvantages: frequent invalidation, update the table, cache all invalidation, resulting in low hit rate, 8.0 was deleted
3. Analyzer:
1, lexical analysis: table names and name analysis
2, mysql syntax analysis
4, optimizer: select index, optimal scheme
5, executor: permission verification, SQL execution