Redis commands: Server and Append

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Redis server

Redis server is a memory-based Key-Value database that is widely used in scenarios such as caching and message queues. Here are some of the main features of Redis server:

1. Fast : The Redis server has fast data reading and writing speed and can handle high concurrent requests.
2. Memory storage : Redis server stores all data in memory, which makes data reading and writing very fast. At the same time, Redis also supports disk-based persistent storage, which can write data to disk regularly.
3. Persistence : Redis server supports disk-based persistent storage, which can write data to disk through snapshots and AOF (Append Only File) mechanisms to ensure that data will not be lost due to server downtime.
4. Scalable : Redis server can be expanded horizontally to improve performance and capacity by increasing the number of servers. At the same time, Redis also supports master-slave replication function, which can realize data backup and fault recovery.
5. Rich data types : Redis server supports multiple data types, including String, List, Set, ZSet and Hash, etc. Each data type has rich operation functions to meet different business needs.
6. Transactions and Lua scripts : Redis server supports transactions and Lua script functions, which can perform complex operations on the server side.
7. Publish and subscribe : The Redis server supports the publish and subscribe function, which can implement the message queue function.
8. Security : Redis server supports password verification and access control list (ACL) functions to protect data security.

In general, the Redis server is a very excellent Key-Value database, suitable for scenarios that require high-performance, low-latency data access and sharing, such as caching, message queues, rankings, etc. At the same time, due to its memory storage characteristics, it is also suitable for big data and high-concurrency processing scenarios.

Example

Here is a simple Redis server example:

1. Start the Redis server : First you need to install Redis and start the Redis server. Redis can be downloaded from the official website. After the installation is completed, the Redis server can be started through the Redis-Server command.
2. Connect to the Redis server : You can use the Redis-Cli tool to connect to the Redis server. Enter the following command at the command line:redis-cli
3. Set key-value pairs : In Redis-Cli, you can use the SET command to set key-value pairs. For example, SET key1 value1.
4. Get the key value : You can use the GET command to get the key value. For example, GET key1.
5. Delete key values : You can use the DEL command to delete key values. For example, DEL key1.
6. Using transactions : You can use the MULTI command to start a transaction and package multiple commands into one transaction. For example, MULTI
   SET key2 value2 EXPIRE key2 10
   SAVE
   DISCARD.
7. Use publish and subscribe : You can use the PUBLISH command to publish messages and the SUBSCRIBE command to subscribe to messages. For example, PUBLISH channel1 "Hello World".

The above is a simple Redis server example. Through this example, you can understand the basic operations and functions of Redis. In practical applications, Redis can be used in conjunction with other programming languages ​​(such as Python, Java, etc.) to implement more complex functions and applications.

Redis server commands

Redis server supports a variety of commands. The following are some commonly used Redis server commands:

1. PING: Test whether the connection to the Redis server is normal. If the server is running and can handle the request normally, it will return PONG.
2. SELECT: Select the database to use. The Redis server has 16 databases by default, numbered from 0 to 15. Use this command to select which database to use to store and retrieve data.
3. SET: Associates a given key with a value, overwriting the old value if the key already exists.
4. GET: Get the value of the specified key.
5. DEL: Delete the given key and its associated value.
6. EXISTS: Checks whether the given key exists.
7. TYPE: Returns the type of the specified key.
8. KEYS: Returns the names of all keys matching the given pattern.
9. COUNT: Returns the number of keys in the current database.
10. FLUSHDB: Delete all keys in the currently selected database.
11. INFO: Provides information and statistics about the server.
12. QUIT: Quit the connection.
13. MONITOR: Real-time dump of received requests.
14. config get: Get server configuration information. For example, config get dir can obtain the value of the parameter configuration dir, and config get* can obtain all parameter configurations.

These commands cover the basic use of Redis server, including operations such as storing, retrieving, deleting and configuring data. In practical applications, more advanced functions and features can also be used in combination with programming languages.

Redis Append

The APPEND command of Redis is used to append another string value to the end of a string value. If the string value does not exist, a new string value will be created and the append operation will be performed; if the key already exists, the append operation will add new string content at the end of the original string value. The APPEND command has the following characteristics:

1. The append operation of string values ​​is atomic, that is, when multiple clients perform append operations on the same string value at the same time, Redis can ensure the order and integrity of the operations and avoid data damage or data loss.
2. The APPEND command supports variable-length strings. You can append string content of any length to the end of the string value without specifying the length of the string in advance.
3. The time complexity of the APPEND command is O(1), that is, constant level. Because Redis stores string values ​​​​in memory, performing string append operations in memory is very fast.
4. The APPEND command also supports the simultaneous append operation of multiple string values, that is, appending multiple strings to the end of the same string value at one time.

Example

The following is an example of the Redis APPEND command:

Suppose we have a key named "mykey" with the corresponding value "Hello". Now, we want to append "World!" to the end of this string value.

First, we use the SET command to set the initial value "Hello" to the "mykey" key:

SET mykey "Hello"

Next, we use the APPEND command to append "World!" to the end of the "mykey" key:

APPEND mykey " World!"

Now, the value of the "mykey" key will become "Hello World!". We can use the GET command to verify this result:

GET mykey

The above command will return "Hello World!" as the result.