SPOP · Valkey

SPOP

Returns one or more random members from a set after removing them. Deletes the set if the last member was popped.

Usage

SPOP key [count]

Description

Removes and returns one or more random members from the set value store at key.

This operation is similar to SRANDMEMBER, that returns one or more random elements from a set but does not remove it.

By default, the command pops a single member from the set. When provided with the optional count argument, the reply will consist of up to count members, depending on the set’s cardinality.

Reply RESP2

One of the following:

Nil reply: if the key does not exist.
Bulk string reply: when called without the count argument, the removed member.
Array reply: when called with the count argument, a list of the removed members.

Reply RESP3

One of the following:

Null reply: if the key does not exist.
Bulk string reply: when called without the count argument, the removed member.
Set reply: when called with the count argument, the set of removed members.

Complexity

Without the count argument O(1), otherwise O(N) where N is the value of the passed count.

ACL Categories

@fast @set @write

Examples

127.0.0.1:6379> SADD myset "one"
(integer) 1
127.0.0.1:6379> SADD myset "two"
(integer) 1
127.0.0.1:6379> SADD myset "three"
(integer) 1
127.0.0.1:6379> SPOP myset
"three"
127.0.0.1:6379> SMEMBERS myset
1) "one"
2) "two"
127.0.0.1:6379> SADD myset "four"
(integer) 1
127.0.0.1:6379> SADD myset "five"
(integer) 1
127.0.0.1:6379> SPOP myset 3
1) "one"
2) "four"
3) "five"
127.0.0.1:6379> SMEMBERS myset
1) "two"

Distribution of returned elements

Note that this command is not suitable when you need a guaranteed uniform distribution of the returned elements. For more information about the algorithms used for SPOP, look up both the Knuth sampling and Floyd sampling algorithms.

History

1.0.0: Introduced.
3.2.0: Added the count argument.