The most direct way to list all keys in the Redis database is to use the KEYS * command, but it is recommended to use the SCAN command to traverse step by step in production environments. 1. The KEYS command is suitable for small or test environments, but may block services; 2. SCAN is an incremental iterator to avoid performance problems and is recommended for production environments; 3. You can switch databases through SELECT and check the keys of different databases one by one; 4. The production environment should also pay attention to key namespace management, regular export of key lists, and use monitoring tools to assist operations.

The most straightforward way to list all keys in the Redis database is to use the KEYS command. For example, running KEYS * will return all matching keys in the current database. However, in actual environments, especially in production environments, this method is not always recommended.

Here are some questions and corresponding suggestions that you may be concerned about:

Use the KEYS command to quickly get all keys

If you are just operating in a small or test-based Redis instance, you can use:

 KEYS *

This command lists all keys in the current database. You can also add wildcards to filter, such as:

 KEYS user:*

This lists all keys that start with user:

??Note : If the data volume is large, this command may cause Redis to block and affect performance. Therefore, it is not recommended to use it in production environments.

Replace KEYS with SCAN to traverse keys safer

To avoid blocking, the SCAN command is recommended. It is an incremental iterator that only returns a portion of the key at a time and will not have much impact on performance.

The basic usage is as follows:

 SCAN 0

Redis returns a cursor and a batch of keys. Continue to continue scanning with the returned cursor until the cursor becomes 0.

For example (pseudocode):

 cursor = 0
while cursor != '0':
    cursor, keys = redis.scan(cursor, count=100)
    process(keys)

• count parameter controls the approximate number of returned each time, and the default is 10.
• You can match the match parameters for pattern matching, such as redis.scan(cursor, match='user:*')

This allows you to gradually obtain all keys without affecting the service.

Pay attention to the database numbering problem of Redis

Redis supports multiple logical databases (there are 16 by default), and the keys between each database are isolated from each other. When you execute KEYS or SCAN , it will only affect the currently selected database.

If you want to confirm which database you are in, you can use:

 SELECT 0

Switch to database No. 0, or select another number as needed.

If you are not sure whether a key exists or belongs to which database, you may need to check the contents of different databases one by one.

Precautions for production environment

In a production environment, it is a risky thing to list all keys directly, especially when the data volume is large. In addition to avoiding KEYS , you can also consider the following points:

• Limit the namespace of key : for example, add a unified prefix to facilitate filtering through SCAN or KEYS .
• Regularly export key lists : keys can be saved to external storage regularly through scripts for easier subsequent analysis.
• Monitoring and auditing tools : Some Redis management tools (such as RedisInsight, phpRedisAdmin) provide visual key browsing functions, which can achieve similar effects.

Basically these are the methods. Although it seems simple, in actual use, you still need to choose the appropriate method based on specific scenarios.

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