VRANDMEMBER

VRANDMEMBER key [count]

Available since:

Redis Open Source 8.0.0

Time complexity:

O(N) where N is the absolute value of the count argument.

Return one or more random elements from a vector set.

The behavior is similar to the SRANDMEMBER command:

• When called without a count, returns a single element as a bulk string.
• When called with a positive count, returns up to that many distinct elements (no duplicates).
• When called with a negative count, returns that many elements, possibly with duplicates.
• If the count exceeds the number of elements, the entire set is returned.
• If the key does not exist, the command returns null if no count is given, or an empty array if a count is provided.

VADD vset VALUES 3 1 0 0 elem1
VADD vset VALUES 3 0 1 0 elem2
VADD vset VALUES 3 0 0 1 elem3

Return a single random element:

VRANDMEMBER vset
"elem2"

Return two distinct random elements:

VRANDMEMBER vset 2
1) "elem1"
2) "elem3"

Return 3 random elements with possible duplicates:

VRANDMEMBER vset -3
1) "elem2"
2) "elem2"
3) "elem1"

Request more elements than exist in the set:

VRANDMEMBER vset 10
1) "elem1"
2) "elem2"
3) "elem3"

When the key doesn't exist:

VRANDMEMBER nonexistent
(nil)

VRANDMEMBER nonexistent 3
(empty array)

This command is useful for:

• Sampling elements for testing or training.
• Generating random queries for performance testing.

Internally:

• For small counts (less than 20% of the set size), a dictionary is used to ensure uniqueness.
• For large counts (more than 20% of the set size), a linear scan provides faster performance, though results may be less random.

Required arguments

Optional arguments

Related topics

• Vector sets

Return information