How does MySQL execute an SQL statement?

hold sql There are two kinds of statements ： Inquire about and to update . Let's talk about it separately .

Query statement

1. Connector operation , Determine the account and password , Query user permissions .
2. The query cache , If there is no cache, it is going down . If there is , Direct return .（MySQL8.0 Then there is no such step ）
3. The analyzer analyzes sql Is the statement legal , And get the function of the sentence .
4. Optimizer optimization SQL sentence , For example, adjust the index order .
5. The actuator first determines whether the user has permission , Then invoke the engine. , Return the execution result of the engine or return error information .

UPDATE statement

1. First query the data to be updated
2. Get the query statement , Make changes .
3. call API Interface , Write this line of data ,InnoDB The engine saves the data in memory , Simultaneous recording redo log. here redo log Enter as prepare state .
4. Send completion to the actuator , Signals that can be submitted .
5. Actuator record binlog.
6. Call engine interface , Submit  redo log Is submitted status .

there redo log and binlog What is it? ？ And why two log modules are used , You can refer to the blog below .

InnoDB Engine MySQL Log module _ The blog of the early rising King -CSDN Blog InnoDB Engine MySQL Log module https://blog.csdn.net/qq_57014350/article/details/122911738

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