Complete process of MySQL SQL

mysql client and mysql server When communicating , If you finish all the MySQL Server modular , It needs to pass through the connector in turn 、 Parser 、 Optimizer 、 actuator 、 Storage engine , As shown in the figure below ：

• The connector ： Use TCP Encrypted ssl Communication protocol , Manage connections , Control the maximum connection amount , Test connection duration , Authority verification （ Account password, etc ）, Priority query cache （ Twice the same select There are update operations between , The query cache will be emptied ）
• Parser ： The same role as the compiler , To generate a syntax tree , analysis SQL Lexical and grammatical analysis
• Optimizer ： Generate SQL Implementation plan and current SQL Selection of corresponding index （explain You can see ）
• actuator ： Call the storage engine corresponding API Interface to read and write data
• Storage engine ： Cost disk I/O Read and write disk data , structure B+ Tree index , Transaction log （undo log/redo log）, Locking mechanism , Isolation level …

class BaseEngine{
    }

class MyISAM : public BaseEngine{
    }
class InnoDB : public BaseEngine{
    }

If a simple communication , The client will actively close the connection after receiving the result of this communication ,MySQL Server The connector is responsible for closing this connection , Recycle the resources of this connection .