Sets

Set Commands

Sets are unordered collections of unique strings. They support fast membership testing, set operations (union, intersection, difference), and random element retrieval.

SADD

Synopsis: SADD key member [member ...]

Add one or more members to a set. Creates the set if it does not exist. Returns the number of members that were added (ignoring members already present).

> SADD myset "a" "b" "c"
(integer) 3
> SADD myset "c" "d"
(integer) 1

SREM

Synopsis: SREM key member [member ...]

Remove one or more members from a set. Returns the number of members that were removed.

> SADD myset "a" "b" "c"
(integer) 3
> SREM myset "b" "d"
(integer) 1

SMEMBERS

Synopsis: SMEMBERS key

Return all members of a set.

> SADD myset "a" "b" "c"
(integer) 3
> SMEMBERS myset
1) "a"
2) "b"
3) "c"

SISMEMBER

Synopsis: SISMEMBER key member

Determine whether a member belongs to a set. Returns 1 if the member exists, 0 otherwise.

> SADD myset "a" "b"
(integer) 2
> SISMEMBER myset "a"
(integer) 1
> SISMEMBER myset "z"
(integer) 0

SMISMEMBER

Synopsis: SMISMEMBER key member [member ...]

Check membership for multiple members at once. Returns an array of 0/1 values.

> SADD myset "a" "b"
(integer) 2
> SMISMEMBER myset "a" "z" "b"
1) (integer) 1
2) (integer) 0
3) (integer) 1

SCARD

Synopsis: SCARD key

Return the number of members in a set (the cardinality).

> SADD myset "a" "b" "c"
(integer) 3
> SCARD myset
(integer) 3

SPOP

Synopsis: SPOP key [count]

Remove and return one or more random members from a set.

> SADD myset "a" "b" "c" "d"
(integer) 4
> SPOP myset
"c"
> SPOP myset 2
1) "a"
2) "d"

SRANDMEMBER

Synopsis: SRANDMEMBER key [count]

Return one or more random members from a set without removing them.

• Positive count: return up to count distinct members.
• Negative count: return |count| members, possibly with duplicates.

> SADD myset "a" "b" "c"
(integer) 3
> SRANDMEMBER myset
"b"
> SRANDMEMBER myset 2
1) "a"
2) "c"

SUNION

Synopsis: SUNION key [key ...]

Return the union of all given sets.

> SADD set1 "a" "b"
(integer) 2
> SADD set2 "b" "c"
(integer) 2
> SUNION set1 set2
1) "a"
2) "b"
3) "c"

SINTER

Synopsis: SINTER key [key ...]

Return the intersection of all given sets.

> SADD set1 "a" "b" "c"
(integer) 3
> SADD set2 "b" "c" "d"
(integer) 3
> SINTER set1 set2
1) "b"
2) "c"

SDIFF

Synopsis: SDIFF key [key ...]

Return the difference between the first set and all subsequent sets.

> SADD set1 "a" "b" "c"
(integer) 3
> SADD set2 "b" "c" "d"
(integer) 3
> SDIFF set1 set2
1) "a"

SUNIONSTORE

Synopsis: SUNIONSTORE destination key [key ...]

Compute the union of all given sets and store the result in destination. Returns the cardinality of the resulting set.

> SADD set1 "a" "b"
(integer) 2
> SADD set2 "b" "c"
(integer) 2
> SUNIONSTORE result set1 set2
(integer) 3

SINTERSTORE

Synopsis: SINTERSTORE destination key [key ...]

Compute the intersection of all given sets and store the result in destination. Returns the cardinality of the resulting set.

> SADD set1 "a" "b" "c"
(integer) 3
> SADD set2 "b" "c" "d"
(integer) 3
> SINTERSTORE result set1 set2
(integer) 2

SDIFFSTORE

Synopsis: SDIFFSTORE destination key [key ...]

Compute the difference between the first set and all subsequent sets, storing the result in destination. Returns the cardinality of the resulting set.

> SADD set1 "a" "b" "c"
(integer) 3
> SADD set2 "b" "c" "d"
(integer) 3
> SDIFFSTORE result set1 set2
(integer) 1

SMOVE

Synopsis: SMOVE source destination member

Atomically move a member from one set to another. Returns 1 if the member was moved, 0 if it was not found in the source set.

> SADD src "a" "b"
(integer) 2
> SADD dst "c"
(integer) 1
> SMOVE src dst "b"
(integer) 1
> SMEMBERS dst
1) "b"
2) "c"

SINTERCARD

Synopsis: SINTERCARD numkeys key [key ...] [LIMIT limit]

Return the cardinality of the intersection of the given sets. The optional LIMIT stops counting once the limit is reached (useful for large sets).

> SADD set1 "a" "b" "c"
(integer) 3
> SADD set2 "b" "c" "d"
(integer) 3
> SINTERCARD 2 set1 set2
(integer) 2
> SINTERCARD 2 set1 set2 LIMIT 1
(integer) 1

SSCAN

Synopsis: SSCAN key cursor [MATCH pattern] [COUNT count]

Incrementally iterate over members of a set.

> SADD myset "a" "b" "c"
(integer) 3
> SSCAN myset 0 MATCH "*" COUNT 10
1) "0"
2) 1) "a"
   2) "b"
   3) "c"