ZRANK and ZREVRANK for position in Redis

Introduction

ZRANK and ZREVRANK help you find the position of an item in a sorted list, so you know where it stands compared to others.

You want to see a player's rank in a game leaderboard.

You need to find the position of a product in a list sorted by price.

You want to check the order of tasks by priority in a to-do list.

You want to know the rank of a student based on their score.

You want to find the position of a word in a sorted dictionary.

Syntax

Redis

ZRANK key member
ZREVRANK key member

ZRANK returns the position of the member with scores ordered from low to high (0 is the top).

ZREVRANK returns the position with scores ordered from high to low (0 is the top).

Examples

Finds the rank of 'player1' in 'leaderboard' sorted from lowest to highest score.

Redis

ZRANK leaderboard player1

Finds the rank of 'player1' in 'leaderboard' sorted from highest to lowest score.

Redis

ZREVRANK leaderboard player1

Gets the position of 'item42' in the sorted set 'scores' from low to high.

Redis

ZRANK scores item42

Sample Program

We add three players with scores. Then we find player3's rank from low to high and from high to low.

Redis

ZADD leaderboard 100 player1 200 player2 150 player3
ZRANK leaderboard player3
ZREVRANK leaderboard player3

Important Notes

If the member does not exist, both commands return null (no rank).

Ranks start at 0, so the top item has rank 0.

ZRANK and ZREVRANK are fast even with many items.

Summary

ZRANK shows position with lowest score first (ascending).

ZREVRANK shows position with highest score first (descending).

Both help find where an item stands in a sorted set.