search
HomeDatabaseMysql Tutorial记一次mysql的调优_MySQL

bitsCN.com

问题现象

mysql CPU占用188%(多核)

解决方法

1.跟踪慢查询

vi /etc/my.cnf 在mysqld下增加如下内容
 

log-slow-queries = slow.log
long_query_time = 5

含义为记录查询时间超过5秒的SQL到slow.log
查找slow.log的内容,发现里面有大量的SQL,下面有几个SQL优化原则
a) 对where语句的字段进行建索引,假定如下SQL为slow.log的内容
select count(*) from table where table_column=‘test’

那么就要对该table_column建立索引(这只是一个普遍的规则,详细规则请到网上查)

建立了索引以后,修改一下mysql的参数

 2.调整mysql参数

    vi /etc/my.cnf

    在[mysqld]下增加如下
    tmp_table_size=1024M

    增加完毕后重启mysql,再进行观察,如果还是负载很高,可以适当调高,我将这个参数调整到2048后负载就下来了

    这个参数值应该根据具体情况具体对待,没有一个特定的值。

    那么这个参数到底是干什么用的呢?为什么如此神奇?哈哈,当执行一个查询,如果SQL对查询进行group by 或者orderby的时候都会将结果集放在这个空间中,因此说如果这个参数很小的话,就会出现上面的问题了~~

 

bitsCN.com
Statement
The content of this article is voluntarily contributed by netizens, and the copyright belongs to the original author. This site does not assume corresponding legal responsibility. If you find any content suspected of plagiarism or infringement, please contact admin@php.cn
How does MySQL index cardinality affect query performance?How does MySQL index cardinality affect query performance?Apr 14, 2025 am 12:18 AM

MySQL index cardinality has a significant impact on query performance: 1. High cardinality index can more effectively narrow the data range and improve query efficiency; 2. Low cardinality index may lead to full table scanning and reduce query performance; 3. In joint index, high cardinality sequences should be placed in front to optimize query.

MySQL: Resources and Tutorials for New UsersMySQL: Resources and Tutorials for New UsersApr 14, 2025 am 12:16 AM

The MySQL learning path includes basic knowledge, core concepts, usage examples, and optimization techniques. 1) Understand basic concepts such as tables, rows, columns, and SQL queries. 2) Learn the definition, working principles and advantages of MySQL. 3) Master basic CRUD operations and advanced usage, such as indexes and stored procedures. 4) Familiar with common error debugging and performance optimization suggestions, such as rational use of indexes and optimization queries. Through these steps, you will have a full grasp of the use and optimization of MySQL.

Real-World MySQL: Examples and Use CasesReal-World MySQL: Examples and Use CasesApr 14, 2025 am 12:15 AM

MySQL's real-world applications include basic database design and complex query optimization. 1) Basic usage: used to store and manage user data, such as inserting, querying, updating and deleting user information. 2) Advanced usage: Handle complex business logic, such as order and inventory management of e-commerce platforms. 3) Performance optimization: Improve performance by rationally using indexes, partition tables and query caches.

SQL Commands in MySQL: Practical ExamplesSQL Commands in MySQL: Practical ExamplesApr 14, 2025 am 12:09 AM

SQL commands in MySQL can be divided into categories such as DDL, DML, DQL, DCL, etc., and are used to create, modify, delete databases and tables, insert, update, delete data, and perform complex query operations. 1. Basic usage includes CREATETABLE creation table, INSERTINTO insert data, and SELECT query data. 2. Advanced usage involves JOIN for table joins, subqueries and GROUPBY for data aggregation. 3. Common errors such as syntax errors, data type mismatch and permission problems can be debugged through syntax checking, data type conversion and permission management. 4. Performance optimization suggestions include using indexes, avoiding full table scanning, optimizing JOIN operations and using transactions to ensure data consistency.

How does InnoDB handle ACID compliance?How does InnoDB handle ACID compliance?Apr 14, 2025 am 12:03 AM

InnoDB achieves atomicity through undolog, consistency and isolation through locking mechanism and MVCC, and persistence through redolog. 1) Atomicity: Use undolog to record the original data to ensure that the transaction can be rolled back. 2) Consistency: Ensure the data consistency through row-level locking and MVCC. 3) Isolation: Supports multiple isolation levels, and REPEATABLEREAD is used by default. 4) Persistence: Use redolog to record modifications to ensure that data is saved for a long time.

MySQL's Place: Databases and ProgrammingMySQL's Place: Databases and ProgrammingApr 13, 2025 am 12:18 AM

MySQL's position in databases and programming is very important. It is an open source relational database management system that is widely used in various application scenarios. 1) MySQL provides efficient data storage, organization and retrieval functions, supporting Web, mobile and enterprise-level systems. 2) It uses a client-server architecture, supports multiple storage engines and index optimization. 3) Basic usages include creating tables and inserting data, and advanced usages involve multi-table JOINs and complex queries. 4) Frequently asked questions such as SQL syntax errors and performance issues can be debugged through the EXPLAIN command and slow query log. 5) Performance optimization methods include rational use of indexes, optimized query and use of caches. Best practices include using transactions and PreparedStatemen

MySQL: From Small Businesses to Large EnterprisesMySQL: From Small Businesses to Large EnterprisesApr 13, 2025 am 12:17 AM

MySQL is suitable for small and large enterprises. 1) Small businesses can use MySQL for basic data management, such as storing customer information. 2) Large enterprises can use MySQL to process massive data and complex business logic to optimize query performance and transaction processing.

What are phantom reads and how does InnoDB prevent them (Next-Key Locking)?What are phantom reads and how does InnoDB prevent them (Next-Key Locking)?Apr 13, 2025 am 12:16 AM

InnoDB effectively prevents phantom reading through Next-KeyLocking mechanism. 1) Next-KeyLocking combines row lock and gap lock to lock records and their gaps to prevent new records from being inserted. 2) In practical applications, by optimizing query and adjusting isolation levels, lock competition can be reduced and concurrency performance can be improved.

See all articles

Hot AI Tools

Undresser.AI Undress

Undresser.AI Undress

AI-powered app for creating realistic nude photos

AI Clothes Remover

AI Clothes Remover

Online AI tool for removing clothes from photos.

Undress AI Tool

Undress AI Tool

Undress images for free

Clothoff.io

Clothoff.io

AI clothes remover

AI Hentai Generator

AI Hentai Generator

Generate AI Hentai for free.

Hot Article

R.E.P.O. Energy Crystals Explained and What They Do (Yellow Crystal)
3 weeks agoBy尊渡假赌尊渡假赌尊渡假赌
R.E.P.O. Best Graphic Settings
3 weeks agoBy尊渡假赌尊渡假赌尊渡假赌
R.E.P.O. How to Fix Audio if You Can't Hear Anyone
4 weeks agoBy尊渡假赌尊渡假赌尊渡假赌
WWE 2K25: How To Unlock Everything In MyRise
1 months agoBy尊渡假赌尊渡假赌尊渡假赌

Hot Tools

Dreamweaver CS6

Dreamweaver CS6

Visual web development tools

VSCode Windows 64-bit Download

VSCode Windows 64-bit Download

A free and powerful IDE editor launched by Microsoft

Dreamweaver Mac version

Dreamweaver Mac version

Visual web development tools

MinGW - Minimalist GNU for Windows

MinGW - Minimalist GNU for Windows

This project is in the process of being migrated to osdn.net/projects/mingw, you can continue to follow us there. MinGW: A native Windows port of the GNU Compiler Collection (GCC), freely distributable import libraries and header files for building native Windows applications; includes extensions to the MSVC runtime to support C99 functionality. All MinGW software can run on 64-bit Windows platforms.

SAP NetWeaver Server Adapter for Eclipse

SAP NetWeaver Server Adapter for Eclipse

Integrate Eclipse with SAP NetWeaver application server.