High Performance My SQL THIRD EDITION
Each client connection gets its own thread within the server process. The connection’s
queries execute within that single thread, which in turn resides on one core or CPU.
The server caches threads, so they don’t need to be created and destroyed for each new
connection.
每个客户端的连接在数据库服务器的进程中有自己的一个线程，单线程。
数据库服务器缓存线程，所以对于每个连接不必创建和销毁，相应的线程不必创建和销毁。
When clients (applications) connect to the My SQL server, the server needs to authen-
ticate them. Authentication is based on username, originating host, and password.
X.509 certificates can also be used across an SSL (Secure Sockets Layer) connection.
Once a client has connected, the server verifies whether the client has privileges for
each query it issues (e.g., whether the client is allowed to issue a S
ELECT statement that
accesses the C
ountry table in the
world database).