SMEMBERS to list all in Redis - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ query_result

intermediate

What is the output of SMEMBERS command?

Given a Redis set stored with key fruits containing apple, banana, and cherry, what will the command SMEMBERS fruits return?

Redis

SMEMBERS fruits

A Error: key does not exist

B ["apple", "banana"]

C ["apple", "banana", "cherry"]

D ["apple"]

💡 Hint

SMEMBERS returns all members of the set stored at the key.

SMEMBERS returns all elements in the set stored at the given key. Since the set contains apple, banana, and cherry, all three are returned.

🧠 Conceptual

intermediate

What type of data structure does SMEMBERS work on?

The Redis command SMEMBERS is used to list all elements of which Redis data type?

A Set

B List

C Hash

D Sorted Set

💡 Hint

SMEMBERS is related to a collection of unique elements.

SMEMBERS works on Redis sets, which are unordered collections of unique strings.

📝 Syntax

advanced

Which command syntax correctly lists all members of a set named 'colors'?

Choose the correct Redis command to list all members of the set stored under the key colors.

A SMEMBERS colors

B SGET colors

C GET colors

D HGETALL colors

💡 Hint

The command starts with 'S' and lists members of a set.

SMEMBERS is the correct command to get all members of a set. SGET and GET are invalid for sets, and HGETALL is for hashes.

❓ query_result

advanced

What happens if SMEMBERS is run on a non-existent key?

If you run SMEMBERS unknown_key where unknown_key does not exist in Redis, what is the output?

A A list with one empty string [""]

B Error: key does not exist

C null

D An empty list []

💡 Hint

Redis returns empty collections for non-existent keys of that type.

SMEMBERS returns an empty list if the key does not exist or is empty.

❓ optimization

expert

How to efficiently retrieve all members of a very large set without blocking Redis?

You have a very large Redis set with millions of members under key bigset. Using SMEMBERS bigset can block Redis for a long time. Which approach is best to retrieve all members without blocking?

A Use SMEMBERS bigset but limit the output with COUNT option

B Use SSCAN bigset with a cursor to iterate in small batches

C Use LRANGE bigset 0 -1 to get all members

D Use HGETALL bigset to get all members

💡 Hint

Use a cursor-based iterator to avoid blocking.

SSCAN allows incremental iteration over large sets without blocking Redis, unlike SMEMBERS which returns all at once.