In Redis, the ZREMRANGEBYRANK command enables us to remove all members from a sorted set with a rank between a certain range.

Syntax

The syntax goes like this:

ZREMRANGEBYRANK key start stop

Example

Suppose we create a sorted set like this:

ZADD cats 15 Meow 27 Fluffy 43 Scratch 84 Purr 25 Bite 37 Bunting

In my case the sorted set didn’t exist, and so it was created and the members were added as specified.

We can use ZRANGE to view all the contents of our sorted set, along with their scores:

ZRANGE cats 0 -1 WITHSCORES

Result:

 1) "Meow"
 2) "15"
 3) "Bite"
 4) "25"
 5) "Fluffy"
 6) "27"
 7) "Bunting"
 8) "37"
 9) "Scratch"
10) "43"
11) "Purr"
12) "84"

Now let’s use the ZREMRANGEBYRANK command to remove one or more of the members from that sorted set, based on its rank being in a certain range:

ZREMRANGEBYRANK cats 1 3

Result:

(integer) 3

The integer reply of 3 tells us that three elements were removed.

Let’s check the contents of the sorted set again:

ZRANGE cats 0 -1 WITHSCORES

Result:

1) "Meow"
2) "15"
3) "Scratch"
4) "43"
5) "Purr"
6) "84"

We can see that Bite, Fluffy, and Bunting no longer exist in the sorted set.

Note that it’s the rank that we’re specifying, not the score. To remove members based on their score, we can use the ZREMRANGEBYSCORE command.

Negative Indexes

We can use negative indexes to remove members with the highest rank.

Negative indexes work backwards from the highest rank. For example, an index of -1 is the last member, -2 is the second last, and so on.

Example:

ZREMRANGEBYRANK cats -2 -1

Result:

(integer) 2

Let’s check the remaining contents:

ZRANGE cats 0 -1

Result:

1) "Meow"

Only one member remains, and it’s the member that had the lowest rank. That’s because we removed the two highest members in our previous operation.

When the Key Doesn’t Exist

If the key doesn’t exist, no operation takes place and we get an integer reply of zero:

ZREMRANGEBYRANK oops 1 3

Result:

(integer) 0

This time nothing was removed, because the oops key didn’t actually exist.

We can use the EXISTS command to check for the existence of a key:

EXISTS oops

Result:

(integer) 0

An integer reply of zero means that it doesn’t exist.

Wrong Data Type

If the key exists, but it holds a different data type, an error occurs:

ZREMRANGEBYRANK animals 1 3

Result:

(error) WRONGTYPE Operation against a key holding the wrong kind of value

In this case, the animals key holds a set (not a sorted set), and so an error occurred.

We can use the TYPE command to check the key’s data type:

TYPE animals

Result:

set

As suspected, it’s a set.