如果 MySQL 数据库比较大的话,我们很容易就能查出是哪些表占用的空间;不过如果 Redis 内存比较大的话,我们就不太容易查出是哪
如果 MySQL 数据库比较大的话,我们很容易就能查出是哪些表占用的空间;不过如果 Redis 内存比较大的话,我们就不太容易查出是哪些(种)键占用的空间了。
有一些工具能够提供必要的帮助,比如 redis-rdb-tools 可以直接分析 RDB 文件来生成报告,可惜它不能百分百实现我的需求,而我也不想在它的基础上二次开发。实际上开发一个专用工具非常简单,利用 SCAN 和 DEBUG 等命令,没多少行代码就能实现:
setOption(Redis::OPT_SCAN, Redis::SCAN_RETRY); $result = array_fill_keys($patterns, 0); while ($keys = $redis->scan($it, $match = '*', $count = 1000)) { foreach ($keys as $key) { foreach ($patterns as $pattern) { if (preg_match("/^{$pattern}$/", $key)) { if ($v = $redis->debug($key)) { $result[$pattern] += $v['serializedlength']; } break; } } } } var_dump($result); ?>当然,前提是你需要提前总结出可能的键模式,,简单但不严谨的方法是 MONITOR:
shell> /path/to/redis-cli monitor | awk -F '"' '$2 ~ "ADD|SET|STORE|PUSH" {print $4}'此外,需要注意的是:因为 DEBUG 返回的 serializedlength 是序列化后的长度,所以最终计算的值小于实际内存占用,但考虑到相对大小依然是有参考意义的。
Ubuntu 14.04下Redis安装及简单测试
Redis集群明细文档
Ubuntu 12.10下安装Redis(图文详解)+ Jedis连接Redis
Redis系列-安装部署维护篇
CentOS 6.3安装Redis
Redis安装部署学习笔记
Redis配置文件redis.conf 详解
Redis 的详细介绍:请点这里
Redis 的下载地址:请点这里
本文永久更新链接地址:

InnoDB uses redologs and undologs to ensure data consistency and reliability. 1.redologs record data page modification to ensure crash recovery and transaction persistence. 2.undologs records the original data value and supports transaction rollback and MVCC.

Key metrics for EXPLAIN commands include type, key, rows, and Extra. 1) The type reflects the access type of the query. The higher the value, the higher the efficiency, such as const is better than ALL. 2) The key displays the index used, and NULL indicates no index. 3) rows estimates the number of scanned rows, affecting query performance. 4) Extra provides additional information, such as Usingfilesort prompts that it needs to be optimized.

Usingtemporary indicates that the need to create temporary tables in MySQL queries, which are commonly found in ORDERBY using DISTINCT, GROUPBY, or non-indexed columns. You can avoid the occurrence of indexes and rewrite queries and improve query performance. Specifically, when Usingtemporary appears in EXPLAIN output, it means that MySQL needs to create temporary tables to handle queries. This usually occurs when: 1) deduplication or grouping when using DISTINCT or GROUPBY; 2) sort when ORDERBY contains non-index columns; 3) use complex subquery or join operations. Optimization methods include: 1) ORDERBY and GROUPB

MySQL/InnoDB supports four transaction isolation levels: ReadUncommitted, ReadCommitted, RepeatableRead and Serializable. 1.ReadUncommitted allows reading of uncommitted data, which may cause dirty reading. 2. ReadCommitted avoids dirty reading, but non-repeatable reading may occur. 3.RepeatableRead is the default level, avoiding dirty reading and non-repeatable reading, but phantom reading may occur. 4. Serializable avoids all concurrency problems but reduces concurrency. Choosing the appropriate isolation level requires balancing data consistency and performance requirements.

MySQL is suitable for web applications and content management systems and is popular for its open source, high performance and ease of use. 1) Compared with PostgreSQL, MySQL performs better in simple queries and high concurrent read operations. 2) Compared with Oracle, MySQL is more popular among small and medium-sized enterprises because of its open source and low cost. 3) Compared with Microsoft SQL Server, MySQL is more suitable for cross-platform applications. 4) Unlike MongoDB, MySQL is more suitable for structured data and transaction processing.

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.

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.

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.


Hot AI Tools

Undresser.AI Undress
AI-powered app for creating realistic nude photos

AI Clothes Remover
Online AI tool for removing clothes from photos.

Undress AI Tool
Undress images for free

Clothoff.io
AI clothes remover

AI Hentai Generator
Generate AI Hentai for free.

Hot Article

Hot Tools

SAP NetWeaver Server Adapter for Eclipse
Integrate Eclipse with SAP NetWeaver application server.

Zend Studio 13.0.1
Powerful PHP integrated development environment

SublimeText3 English version
Recommended: Win version, supports code prompts!

SublimeText3 Chinese version
Chinese version, very easy to use

Dreamweaver Mac version
Visual web development tools