SPOP

Usage:

SPOP key [ count ]

Complexity:

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

Since:

1.0.0

ACL Categories:

@fast, @set, @write

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

One of the following:

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

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

Version	Change
3.2.0	Added the count argument.