Redis的第一步

当你有雷迪斯启动并运行,就可以开始使用它了!

最简单的方法是使用redis-cli,即在安装Redis时安装的应用程序。

这是一种将命令写入Redis的内置方式,而无需为此设置应用程序。

您可以使用以下方式连接到远程Redis服务器redis-cli -h <host> -p <port> -a <password>

进入Redis CLI应用程序后,就可以开始将数据存储到其中了。

使用结构添加值SET <key> <value>

SET name "Flavio"

Retrieve a value

Retrieve a value using the structure GET <key>:

Check if a key exists

We can also check if a key exists using EXISTS <key>:

The command returns either 1 (exists) or 0 (does not exist).

Set if not exists

A variation of SET allows us to only set a key if it does not exist yet:

SETNX name "Roger"

Delete a key

Delete a key using DEL <key>:

Listing existing keys

You can list all keys inserted using KEYS *

Or you can filter using a pattern like KEYS n* to only list keys starting with n, for example.

Each value stored can hold up to 512 MB in value.

Expiring keys

A key can be temporarily stored, and removed automatically when the timer ends:

SETEX <key> <seconds> <value>

You can get the time remaining for a key to be cleared using TTL <key>

In this example I set a name key with Flavio as value, and using TTL I can check how much time is left until the key will return the value. Once the timer expires, it results in a null value (nil):

You can also set an existing key to expire using EXPIRE <key> seconds>.

Increment and decrement

A numeric value can be incremented using INCR <key> and decremented using DECR <key>. You can also use INCRBY <key> <amount> and DECRBY <key> <amount> to increment a key value by a specific amount:

Those commands are very well suited for high concurrent operations where many clients might interact with the same data, to ensure atomic transactions.

The most common example is when 2 different clients try to increment the same number.

On a database like PostgreSQL or MongoDB you first get the number value, you increment it, then you make a request to the server to increment it.

Say the value is 1. If two clients read the value using GET then they call SET to increment it independently, in the end if there is nothing preventing the concurrent change to happen, the result will be 2. Redis prevents this problem at the root.

More complex data structures

So far we’ve worked with simple data types like integers and strings.

Redis can support more complex structures.

Let’s see in the next lessons how to work with:

  • Lists
  • Sets
  • Sorted sets
  • Hashes

More redis tutorials: