EXISTS

The Redis EXISTS command is used to check if given keys exist.

Redis Native Command Syntax

EXISTS key [key ...]

Parameter Description

• key: The key(s) to check for existence, multiple keys can be specified

Detailed Explanation

The EXISTS command checks if one or more keys exist. Starting from Redis 3.0.3, multiple keys can be specified.

If a single key is specified, the command returns 1 if the key exists, 0 if the key does not exist. If multiple keys are specified, the command returns the number of keys that exist.

Redisun Usage

In redisun, the EXISTS command is implemented through the ExistsCommand class and the exists method in the Redisun class.

Synchronous Mode

// Check if a single key exists
int exists = redisun.exists("mykey");

// Check if multiple keys exist
int exists = redisun.exists("mykey1", "mykey2", "mykey3");

Asynchronous Mode

// Check if a single key exists
CompletableFuture<Integer> future = redisun.asyncExists("mykey");

// Check if multiple keys exist
CompletableFuture<Integer> future = redisun.asyncExists("mykey1", "mykey2", "mykey3");

Notes

1. The time complexity of the EXISTS command is O(1).
2. This command is applicable to all types of keys, including strings, hashes, lists, sets, and sorted sets.
3. If a key has expired and been deleted, the EXISTS command will return 0.
4. Starting from Redis 3.0.3, multiple keys can be checked at once, returning the number of keys that exist.

References

• Redis EXISTS Command Official Documentation