Set Operations with Redis Commands

Compared to other Redis data structures, sets are unique in that they’re unordered and contain only unique values. This makes sets a good choice for certain types of data, such as unique IDs or tags. Other Redis data structures, like lists or sorted sets, have different use cases and performance characteristics. Lists, for example, are ordered and allow for efficient insertion and deletion at either end of the list. Here are some ways in which sets are useful in Redis:

• Unique item tracking: Sets are useful for tracking unique items, such as user IDs or product IDs. This can be useful for a variety of purposes, such as counting unique visitors to a website or tracking inventory levels.

• Set operations: Redis provides a variety of set operations, such as union, intersection, and difference, which can be used to perform powerful data manipulations. For example, we can use set operations to find the common items between two sets or remove items from one set that are also present in another set.

Overall, sets are a powerful and versatile data structure in Redis that can be used for a variety of purposes. We’re going to explore the different commands that can be executed when dealing with sets in Redis. We’ll learn the six most commonly used commands to perform set operations, which can be of great help in creating applications with Redis where we want to maintain unique elements only in our Redis data store.

The SADD command

As the name suggests, the SADD command is used to insert data in a set. This command can insert multiple elements and return the number of elements inserted in the current operation.

Syntax and example

The syntax of the SADD command is shown below:

An example of how to store multiple values in a set named ip is given below:

The command above returns an integer 3, even though we tried to insert four elements. Since two of the elements are the same, the set only stores three distinct elements.

The SPOP command

The SPOP command is used to delete a single or even multiple elements from a set. Deletion of elements from the set is done randomly because there’s no ordering of elements in the set. This means that if we try to get the values of a set for the first time, the values most likely won't come in the same order for subsequent retrievals. The SPOP command accepts an optional integer parameter to remove multiple elements from the set and return the removed elements (either a single element or a list of elements). Here are some scenarios where using SPOP to pop a random element from a set could be a good choice in Redis:

• Random sampling: If we have a set of items and we need to select a random sample from that set, we can use SPOP to select a random item and remove it from the set. We can continue to use SPOP to select additional random items until we have the desired sample size. ...