mysql execution process

MySQL is currently the most widely used relational database management system and the preferred database system for most websites and applications. This article will explore the execution process of MySQL.

1. Query statement parsing

After MySQL receives the query request, it will parse the query statement. This process checks whether the syntax of the query statement is correct and determines the query type.

2. Query Optimizer

The query optimizer analyzes and optimizes query statements to ensure that the best query results can be obtained with the least resources. The main task of the optimizer is to determine the execution plan of the query statement.

The query optimizer will optimize based on various factors such as the type of query statement, the size of the table, the condition of the index, and the system load. The optimizer tries to find the best execution plan to improve query performance.

3. Query Executor

The query executor will execute the query statement according to the execution plan generated by the query optimizer. During execution, the executor will send query requests to other components inside the MySQL server to obtain data in the database.

4. Storage Engine

The storage engine is the component in MySQL that actually stores data. MySQL supports a variety of different storage engines, such as InnoDB, MyISAM, Memory, etc.

The query executor will call the storage engine to retrieve data. The storage engine returns the retrieved data to the executor, which then returns the data to the client.

5. Data cache

MySQL's data cache system can improve query performance. When MySQL reads data from the storage engine, it caches the data into memory so that it can be accessed faster later.

Data caching can significantly improve query performance. If a query request accesses data that is already in the cache, the query will be very fast. If the data is not in cache, MySQL needs to fetch the data from disk, which will cause queries to be slower.

6. Log

MySQL also contains multiple types of logs, which are used to record changes in the database for operations such as failure recovery, backup, and replication.

When executing a query, MySQL will record the query request and other changes, such as insert, update, and delete operations. These operations can be recorded to binary log files for data replication from the primary database to the backup database.

Summary

The execution process of MySQL is very complex, including multiple components such as query statement parsing, query optimizer, query executor, storage engine, data cache and log. During the execution process, MySQL will access files, data, indexes and other information in a certain order to generate the final query results. Understanding the execution process of MySQL can help us better optimize database performance.

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