Sets In Redis

In mathematics, a set is a collection of elements. The elements that make up a set can be any kind of mathematical objects: numbers, symbols, points in space, lines, other geometrical shapes, variables, or even other sets. The set with no element is the empty set; a set with a single element is a singleton.

we looked at storing lists of elements in Redis. The problem with a list is that it allows duplicate elements. If we need to add unique elements, we can use a Set instead of a List.

Redis internally uses a hash table to store the elements as a Set. The image below depicts how elements are stored in a Set. There is no particular order. The elements are stored randomly, and repetition is not allowed.

Insertion Commands

1. SADD This command is used to add members to set

SADD key members...

2. SMEMBERS This command is used to view all members in the set

SMEMBERS key

3. SISMEMBER This command is used to check if the member is exists, return 1 if exits, and 0 if not exists

SISMEMBER member

4. SCARD This command is used to get count of members in the set

SCARD key

5. SDIFF This command is used to get the difference between two sets

DIFF key1 key2

Modification Commands

1. SUNION This command is used to to find the union of two sets or more

SUNION key1 key2 key3 ...

2. SREM This command is used to remove member or more from set

SREM key member1 member2 ...

3. SPOP This command is used to remove one or more random members from the set

SPOP key

4. SMOVE This command is used to move member from one set to another.

SMOVE source dest member

You can read more about Redis sets at the official website