XLEN for stream length in Redis - Cheat Sheet & Quick Revision

Recall & Review

beginner

What does the Redis command XLEN do?

The XLEN command returns the number of entries (length) in a Redis stream.

beginner

How do you use XLEN to find the length of a stream named mystream?

Use the command: XLEN mystream. It returns the count of entries in mystream.

intermediate

What will XLEN return if the stream does not exist?

If the stream does not exist, XLEN returns 0, meaning the stream is empty or missing.

beginner

Why is XLEN useful when working with Redis streams?

XLEN helps you quickly check how many messages or events are stored in a stream, useful for monitoring or processing logic.

intermediate

Can XLEN be used to get the size in bytes of a Redis stream?

No, XLEN only returns the number of entries, not the memory size. Use MEMORY USAGE for size in bytes.

What does the Redis command XLEN mystream return?

A The number of entries in the stream named mystream

B The size in bytes of the stream named mystream

C The last entry ID in the stream named mystream

D The first entry ID in the stream named mystream

XLEN returns the count of entries in the specified stream.

If a Redis stream does not exist, what does XLEN return?

A 1

B Null

C An error

D 0

XLEN returns 0 if the stream does not exist.

Which Redis command would you use to find the number of entries in a stream?

A XLEN

B XREAD

C XADD

D XDEL

XLEN returns the length of a stream.

Does XLEN provide the memory size of a stream?

A Yes, it returns size in bytes

B No, it returns number of entries

C Yes, but only for small streams

D No, it returns the last entry ID

XLEN returns the count of entries, not memory size.

Which of these is a valid use of XLEN?

A To delete entries from a stream

B To add new entries to a stream

C To count how many messages are in a Redis stream

D To read entries from a stream

XLEN counts entries; other commands handle adding, deleting, or reading.

Explain what the Redis command XLEN does and when you might use it.

Think about how you check the size of a list or queue.

Describe the difference between XLEN and MEMORY USAGE commands in Redis streams.

One counts items, the other measures space.