ZREM

The ZREM command in DiceDB is used to remove the specified members from the sorted set stored at key and return the number of members removed from the sorted set. This command ignores the non-existing members.

Syntax

ZREM key member [member ...]

Parameters

Parameter	Description	Type	Required	Multiple
key	The key associated with the sorted set whose members are to be removed	String	Yes	No
member	One or more members to remove from the sorted set	String	Yes	Yes

Return Value

Condition	Return Value
If specified key and members exists	Count of members removed from the sorted set at key
If key doesn’t exist	0
If member doesn’t exist	0

Behaviour

• DiceDB checks if the specified key exists.
• If the key exists and is associated with a sorted set, DiceDB removes the members from the sorted set and returns number of members removed.
• If the key does not exist, DiceDB returns 0.
• If the key exists but is not associated with a sorted set, an error is returned.

Errors

1. Wrong type of 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 sorted set value.

2. Wrong number of arguments:

   • Error Message: (error) -ERR wrong number of arguments for 'ZREM' command
   • Occurs if key or member isn’t specified in the command.

Example Usage

Basic Usage

Creating sorted set myzset with fields one, two, three, four, five with scores 1, 2, 3, 4, 5 respectively. Removing elements from myzset.

127.0.0.1:7379> ZADD myzset 1 "one" 2 "two" 3 "three" 4 "four" 5 "five"
(integer) 5
127.0.0.1:7379> ZREM myzset one
(integer) 1
127.0.0.1:7379> ZREM myzset two six
(integer) 1
127.0.0.1:7379> ZREM myzset three four
(integer) 2

Invalid Usage on non-existent sorted set

Removing element from a non-existent sorted set nonExistentZSet.

127.0.0.1:7379> ZREM nonExistentZSet one
(integer) 0

Invalid Usage on a non sorted set key

Getting cardinality of a key mystring associated with a non sorted set type.

127.0.0.1:7379> SET mystring "This is a string"
OK
127.0.0.1:7379> ZREM mystring
(error) WRONGTYPE Operation against a key holding the wrong kind of value

Notes

• The ZREM command is a O(M*log(N)) time-complexity operation, with N being the number of elements in the sorted set and M the number of elements to be removed.