SREM

The SREM command is used to remove one or more members from a set stored at a specified key. If the specified members are not present in the set, they are ignored. If the key does not exist, it is treated as an empty set and the command returns 0. This command is idempotent, meaning that removing a member that does not exist in the set has no effect.

Syntax

SREM key member [member ...]

Parameters

Parameter	Description	Type	Required
key	The key of the set from which the members will be removed. This key must be of the set data type.	String	Yes
member	One or more members to be removed from the set. Multiple members can be specified, separated by spaces.	String	Yes

Return Value

Condition	Return Value
key does not exist	0
key is not a set	error
member does not exist in the set	0
Invalid syntax or no specified keys	error
Members are successfully removed	Integer reply: The number of members that were removed from the set, not including non-existing members.

Behaviour

When the SREM command is executed, the following steps occur:

1. DiceDB checks if the key exists.
2. If the key does not exist, it is treated as an empty set, and the command returns 0.
3. If the key exists but is not of the set data type, an error is returned.
4. DiceDB attempts to remove the specified members from the set.
5. The command returns the number of members that were successfully removed.

Error Handling

• WRONGTYPE Operation against a key holding the wrong kind of value: This error is returned if the key exists but is not of the set data type.
• Syntax error: This error is returned if the command is not used with the correct number of arguments.

Example Usage

Removing a single member from a set

127.0.0.1:7379> SADD myset "one" "two" "three"
127.0.0.1:7379> SREM myset "two"
(integer) 1

The member “two” is removed from the set myset. The command returns 1 because one member was removed.

Removing multiple members from a set

127.0.0.1:7379> SADD myset "one" "two" "three"
127.0.0.1:7379> SREM myset "two" "three"
(integer) 2

The members “two” and “three” are removed from the set myset. The command returns 2 because two members were removed.

Removing members from a non-existing set

127.0.0.1:7379> SREM myset "one"
(integer) 0

The set myset does not exist. The command returns 0 because no members were removed.

Error when key is not a set

127.0.0.1:7379> SET mykey "value"
127.0.0.1:7379> SREM mykey "one"
(error) WRONGTYPE Operation against a key holding the wrong kind of value

The key mykey exists but is not of the set data type. The command returns an error.

Notes

• The SREM command is idempotent. Removing a member that does not exist in the set has no effect and does not produce an error.
• The command can be used to remove multiple members in a single call, which can be more efficient than calling SREM multiple times for individual members.
• If the set becomes empty after the removal of members, the key is automatically deleted from the database.

By understanding the SREM command, you can effectively manage the members of sets in your DiceDB database, ensuring efficient and error-free operations.