Why redis is faster than mysql
Redis puts all data in memory. When non-data synchronization works normally, there is no need to read data from disk, 0 IO times. The memory response time is about 100 nanoseconds, which is an important basis for the fast speed of Redis.
Mysql is a persistent storage, which is stored in the disk. Retrieval will involve a certain amount of IO. In order to solve this bottleneck, caches appeared, such as memcached, which is the most used now. (referred to as mc).
First, the user accesses mc. If it misses, access mysql. Then, like memory and hard disk, the data is copied to the redis part of mc. Both mc and mc are cached and run in memory, which greatly improves the access speed of web access with high data volume. (Recommended learning: Redis video tutorial)
However, mc only provides simple data structures, such as string storage; redis provides a large number of data structures, such as String, list, set, hashset, sorted set, etc., make it a lot more convenient for users. After all, they encapsulate a layer of practical functions and achieve the same effect. Of course, use redis and slowly abandon mc.
Redis is single-threaded. Simplifying the implementation of algorithms, the implementation of concurrent data structures is not only difficult but also troublesome to test. Second, a single thread avoids the consumption caused by thread switching and locking and releasing locks. For server-side development, locks and thread switching are usually performance killers. Of course, single threading will also have its shortcomings, which is also Redis's nightmare: blocking. If the execution of a command is too long, it will cause other commands to be blocked, which is very fatal for Redis, so Redis is a database for fast execution scenarios.
Redis uses epoll as the implementation of I/O multiplexing technology, and Redis's own event processing model converts epoll's read, write, close, etc. into events, not on network I/O Too much time wasted. Realize monitoring of multiple FD reads and writes to improve performance.
Mysql is used to store data persistently on the hard disk. It is powerful but slow.
Redis is used to store frequently used data in the cache and has fast reading speed.
For more Redis-related technical articles, please visit the Introduction Tutorial on Using Redis Database column to learn!
The above is the detailed content of Why redis is faster than mysql. For more information, please follow other related articles on the PHP Chinese website!

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

Video Face Swap
Swap faces in any video effortlessly with our completely free AI face swap tool!

Hot Article

Hot Tools

Notepad++7.3.1
Easy-to-use and free code editor

SublimeText3 Chinese version
Chinese version, very easy to use

Zend Studio 13.0.1
Powerful PHP integrated development environment

Dreamweaver CS6
Visual web development tools

SublimeText3 Mac version
God-level code editing software (SublimeText3)

Hot Topics





Redis cluster mode deploys Redis instances to multiple servers through sharding, improving scalability and availability. The construction steps are as follows: Create odd Redis instances with different ports; Create 3 sentinel instances, monitor Redis instances and failover; configure sentinel configuration files, add monitoring Redis instance information and failover settings; configure Redis instance configuration files, enable cluster mode and specify the cluster information file path; create nodes.conf file, containing information of each Redis instance; start the cluster, execute the create command to create a cluster and specify the number of replicas; log in to the cluster to execute the CLUSTER INFO command to verify the cluster status; make

How to clear Redis data: Use the FLUSHALL command to clear all key values. Use the FLUSHDB command to clear the key value of the currently selected database. Use SELECT to switch databases, and then use FLUSHDB to clear multiple databases. Use the DEL command to delete a specific key. Use the redis-cli tool to clear the data.

To read a queue from Redis, you need to get the queue name, read the elements using the LPOP command, and process the empty queue. The specific steps are as follows: Get the queue name: name it with the prefix of "queue:" such as "queue:my-queue". Use the LPOP command: Eject the element from the head of the queue and return its value, such as LPOP queue:my-queue. Processing empty queues: If the queue is empty, LPOP returns nil, and you can check whether the queue exists before reading the element.

Using the Redis directive requires the following steps: Open the Redis client. Enter the command (verb key value). Provides the required parameters (varies from instruction to instruction). Press Enter to execute the command. Redis returns a response indicating the result of the operation (usually OK or -ERR).

Using Redis to lock operations requires obtaining the lock through the SETNX command, and then using the EXPIRE command to set the expiration time. The specific steps are: (1) Use the SETNX command to try to set a key-value pair; (2) Use the EXPIRE command to set the expiration time for the lock; (3) Use the DEL command to delete the lock when the lock is no longer needed.

The best way to understand Redis source code is to go step by step: get familiar with the basics of Redis. Select a specific module or function as the starting point. Start with the entry point of the module or function and view the code line by line. View the code through the function call chain. Be familiar with the underlying data structures used by Redis. Identify the algorithm used by Redis.

Use the Redis command line tool (redis-cli) to manage and operate Redis through the following steps: Connect to the server, specify the address and port. Send commands to the server using the command name and parameters. Use the HELP command to view help information for a specific command. Use the QUIT command to exit the command line tool.

Redis data loss causes include memory failures, power outages, human errors, and hardware failures. The solutions are: 1. Store data to disk with RDB or AOF persistence; 2. Copy to multiple servers for high availability; 3. HA with Redis Sentinel or Redis Cluster; 4. Create snapshots to back up data; 5. Implement best practices such as persistence, replication, snapshots, monitoring, and security measures.
