ZRANDMEMBER

ZRANDMEMBER key [options]

Available since

6.2.0

Time complexity

O(N) where N is the number of members returned

ACL categories

@read, @sortedset, @slow

When called with just the key argument, return a random element from the sorted set value stored at key.

If the provided count argument is positive, return an array of distinct elements. The array’s length is either count or the sorted set’s cardinality (ZCARD), whichever is lower.

If called with a negative count, the behavior changes and the command is allowed to return the same element multiple times. In this case, the number of returned elements is the absolute value of the specified count.

The optional WITHSCORES modifier changes the reply so it includes the respective scores of the randomly selected elements from the sorted set.

Examples #

ZADD dadi 1 uno 2 due 3 tre 4 quattro 5 cinque 6 sei
ZRANDMEMBER dadi
ZRANDMEMBER dadi
ZRANDMEMBER dadi -5 WITHSCORES

Specification of the behavior when count is passed #

When the count argument is a positive value this command behaves as follows:

• No repeated elements are returned.
• If count is bigger than the cardinality of the sorted set, the command will only return the whole sorted set without additional elements.
• The order of elements in the reply is not truly random, so it is up to the client to shuffle them if needed.

When the count is a negative value, the behavior changes as follows:

• Repeating elements are possible.
• Exactly count elements, or an empty array if the sorted set is empty (non-existing key), are always returned.
• The order of elements in the reply is truly random.