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ZRANDMEMBER

Returns one or more random members from a sorted set without removing them. Optionally, it can also return the scores of the randomly selected members.

Syntax​

ZRANDMEMBER key [count [WITHSCORES]]

Parameters​

  • key: The name of the sorted set.
  • count: Optional. Specifies the number of random members to return. If not provided, a single random member is returned. If count is negative, the command will return the same element multiple times.
  • WITHSCORES: Optional. When specified, the command returns both the members and their scores.

Details​

  • Available since: 6.2.0
  • Time complexity: O(1) if count is 1, otherwise O(N) where N is the absolute value of count.
  • ACL categories: @read, @sortedset, @fast

The ZRANDMEMBER command is used to retrieve random members from the sorted set stored at key. The members are returned without being removed from the sorted set. If count is positive, the command returns a list of distinct elements. If count is negative, the command allows repeated members in the output.

Examples​

Basic Usage​

Assume we have a sorted set called myzset with the following members:

ZADD myzset 1 "a" 2 "b" 3 "c" 4 "d" 5 "e"

To retrieve a single random member:

ZRANDMEMBER myzset

This will return a random member, e.g.,:

"c"

Retrieving Multiple Members​

To retrieve three random members:

ZRANDMEMBER myzset 3

This will return:

1) "b"
2) "d"
3) "a"

Retrieving Multiple Members with Scores​

To retrieve two random members along with their scores:

ZRANDMEMBER myzset 2 WITHSCORES

This will return:

1) "e"
2) "5"
3) "a"
4) "1"

Allowing Repeated Members​

To retrieve three random members, allowing repetition:

ZRANDMEMBER myzset -3

This could return:

1) "b"
2) "b"
3) "d"

Edge Cases​

  • If the key does not exist, ZRANDMEMBER returns a nil reply.
  • If the key exists but is not a sorted set, an error is returned.
  • If count is 0, an empty array is returned.

RESP2/RESP3 Reply​

  • Bulk string reply if count is not specified: a single random member.
  • Array reply if count is specified: a list of random members, optionally with their scores if WITHSCORES is used.