XRANGE and XREVRANGE in Redis - Cheat Sheet & Quick Revision

Recall & Review

beginner

What does the XRANGE command do in Redis Streams?

XRANGE returns a range of entries from a Redis Stream in ascending order by entry ID, between a specified start and end ID.

beginner

How does XREVRANGE differ from XRANGE?

XREVRANGE returns entries from a Redis Stream in descending order by entry ID, between a specified end and start ID.

beginner

What is the format of the IDs used in XRANGE and XREVRANGE commands?

IDs are strings in the format <millisecondsTime>-<sequenceNumber>, for example, '1526985058136-0'.

intermediate

How can you limit the number of entries returned by XRANGE or XREVRANGE?

You can use the COUNT option followed by a number to limit how many entries are returned.

intermediate

What happens if you use '-' and '+' as start and end IDs in XRANGE?

'-' means the smallest ID (start of stream), '+' means the largest ID (end of stream), so XRANGE - + returns all entries in ascending order.

Which command returns Redis Stream entries in descending order?

A XRANGE

B XREAD

C XREVRANGE

D XADD

XREVRANGE returns entries in descending order by ID.

What does the COUNT option do in XRANGE or XREVRANGE?

A Limits the number of entries returned

B Specifies the end ID

C Specifies the start ID

D Deletes entries

COUNT limits how many entries the command returns.

What ID range does XRANGE - + cover?

A From the largest to smallest ID

B From the smallest to largest ID

C Only entries with ID '-' or '+'

D No entries

'-' is smallest ID, '+' is largest ID, so it covers the full stream in ascending order.

Which of these is a valid Redis Stream entry ID?

A 1526985058136-0

B abc-123

C 2023-04-01

D ID_001

Redis Stream IDs are numeric timestamps plus sequence numbers separated by a dash.

If you want entries from newest to oldest, which command do you use?

A XDEL

B XRANGE

C XREAD

D XREVRANGE

XREVRANGE returns entries in reverse order, from newest to oldest.

Explain how XRANGE and XREVRANGE commands work in Redis Streams and when you might use each.

Think about reading messages in order or reverse order.

Describe how to limit the number of entries returned by XRANGE or XREVRANGE and why this might be useful.

Consider performance and data size.