Deleting Redis Keys by Pattern in Java (Detailed Guide w/ Code Examples)

Use Case(s)

This approach is commonly used when there is a need to delete specific keys that match a certain pattern. It can be helpful in scenarios such as cache invalidation, memory cleanup, or data reorganization.

Code Examples

Here is an example using Jedis, a popular Redis Java client:

import redis.clients.jedis.Jedis;
import java.util.Set;

public class Main {
    public static void main(String[] args) {
        // Connect to Redis
        Jedis jedis = new Jedis("localhost");
        
        // Get keys matching pattern
        Set<String> keys = jedis.keys("pattern*");
        
        // Delete keys
        keys.forEach(jedis::del);
       
        jedis.close();
    }
}

In this code, we first connect to the Redis server using the Jedis client. We then retrieve all keys that match the given pattern using the keys method and delete each of these keys using the del method.

Best Practices

Avoid using the KEYS command in production environments as it may negatively affect performance due to its O(N) time complexity. Instead, consider using SCAN or storing your keys in a way that allows you to delete them without having to scan the entire keyspace.

Common Mistakes

One common mistake is not handling exceptions in case the connection to Redis fails, or if there's an error during the deletion process. Always include necessary error handling code.

FAQs

Q: Why are keys deleted by pattern? A: Deleting keys by pattern allows you to target and remove specific subsets of your data. This can be useful when you need to clear out certain caches, or delete temporary data.

Q: What happens if a key does not exist? A: In Redis, if you try to delete a key that doesn't exist, it is simply ignored -- no error will be returned.