EXISTS

The EXISTS command in DiceDB is used to determine if one or more specified keys exist in the database. It returns the number of keys that exist among the specified ones.

Syntax

EXISTS key [key ...]

Parameters

Parameter	Description	Type	Required
key	The key(s) to check for existence. One or more keys can be specified, separated by spaces.	String	Yes

Return values

Condition	Return Value
None of the specified keys exist	0
One or more specified keys exist	Integer representing the count of keys that exist

Behaviour

• The EXISTS command checks whether the specified keys are present in the database.
• Returns 1 or 0, or for multiple keys returns the count of existing keys.
• The command performs a read-only operation and does not modify the database.

Errors

1. Wrong number of arguments:

   • Error Message: (error) ERR wrong number of arguments for 'exists' command
   • Occurs when no key is provided.

2. Wrong type of value or key:

   • Error Message: (error) WRONGTYPE Operation against a key holding the wrong kind of value
   • Occurs when attempting to use the command on a key that contains a non-string value.

Example Usage

Single Key Check

Checking if a key mykey exists in the database:

127.0.0.1:7379> SET mykey "Hello"
OK
127.0.0.1:7379> EXISTS mykey
(integer) 1

Multiple Keys Check

Checking if multiple keys (key1, key2, key3) exist in the database:

127.0.0.1:7379> SET key1 "value1"
OK
127.0.0.1:7379> SET key2 "value2"
OK
127.0.0.1:7379> EXISTS key1 key2 key3
(integer) 2

In this case, key1 and key2 exist, but key3 does not.

Non-Existent Key

Checking if a non-existent key (nonExistentKey) is present in the database:

127.0.0.1:7379> EXISTS nonExistentKey
(integer) 0

All Non-Existent Keys

Checking if all non-existent keys return 0:

127.0.0.1:7379> EXISTS nonExistentKey1 nonExistentKey2
(integer) 0

Empty Command

Providing no keys should trigger an error:

127.0.0.1:7379> EXISTS
(error) ERR wrong number of arguments for 'exists' command