SPOP for random removal in Redis - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ query_result

intermediate

What is the output of the SPOP command?

Given a Redis set myset containing the elements {"apple", "banana", "cherry"}, what will be the result of the command SPOP myset?

Redis

SADD myset apple banana cherry
SPOP myset

A Returns an error because SPOP requires a count argument

B "apple" (or "banana" or "cherry") and the element is removed from the set

C Returns all elements in the set without removing any

D Returns the number of elements in the set

💡 Hint

SPOP removes and returns a random element from the set.

The SPOP command removes and returns one random element from the set. Since the set has three elements, it will return one of them and remove it from the set.

❓ query_result

intermediate

What happens when using SPOP with a count argument?

If myset contains {"a", "b", "c", "d"}, what is the result of SPOP myset 2?

Redis

SADD myset a b c d
SPOP myset 2

A Returns an array of 2 random elements and removes them from the set

B Returns a single random element and ignores the count argument

C Returns all elements in the set without removing any

D Returns an error because count must be 1

💡 Hint

SPOP can take an optional count to remove multiple elements.

When a count is provided, SPOP returns that many random elements and removes them from the set.

📝 Syntax

advanced

Which SPOP command syntax is correct for removing 3 random elements?

Choose the correct Redis command to remove 3 random elements from the set colors.

A SPOP colors -count 3

B SPOP colors REMOVE 3

C SPOP colors COUNT 3

D SPOP colors 3

💡 Hint

SPOP accepts an optional count as a second argument without keywords.

The correct syntax is SPOP key count. Other options are invalid syntax.

🧠 Conceptual

advanced

What happens if the count in SPOP exceeds the set size?

If myset contains 2 elements, what does SPOP myset 5 return?

Redis

SADD myset x y
SPOP myset 5

A Returns all elements in the set and empties the set

B Returns an error because count is larger than set size

C Returns 5 elements with duplicates

D Returns an empty array

💡 Hint

SPOP returns as many elements as possible up to the count.

If count is larger than the set size, SPOP returns all elements and empties the set without error.

🔧 Debug

expert

Why does this SPOP command cause an error?

Given the command SPOP myset two, why does Redis return an error?

Redis

SPOP myset two

A Because SPOP does not accept a count argument

B Because the set 'myset' does not exist

C Because the count argument must be an integer, not a string

D Because the command requires a key and a value

💡 Hint

Count must be a number, not text.

The count argument must be a positive integer. Using a non-integer string causes a syntax error.